diff --git a/100 Numpy exercises with hint.ipynb b/100 Numpy exercises with hint.ipynb
index d9dd849..d1ea964 100644
--- a/100 Numpy exercises with hint.ipynb	
+++ b/100 Numpy exercises with hint.ipynb	
@@ -17,7 +17,7 @@
    "metadata": {},
    "source": [
     "#### 1. Import the numpy package under the name `np` (★☆☆) \n",
-    "##### (hint: import … as ..)"
+    "(**hint**: import ... as ..)"
    ]
   },
   {
@@ -34,7 +34,7 @@
    "metadata": {},
    "source": [
     "#### 2. Print the numpy version and the configuration (★☆☆) \n",
-    "##### (hint: np.\\_\\_verison\\_\\_, np.show\\_config)"
+    "(**hint**: np.\\_\\_verison\\_\\_, np.show\\_config)"
    ]
   },
   {
@@ -51,7 +51,7 @@
    "metadata": {},
    "source": [
     "#### 3. Create a null vector of size 10 (★☆☆) \n",
-    "##### (hint: np.zeros)"
+    "(**hint**: np.zeros)"
    ]
   },
   {
@@ -68,7 +68,7 @@
    "metadata": {},
    "source": [
     "#### 4.  How to find the memory size of any array (★☆☆) \n",
-    "##### (hint: size, itemsize)"
+    "(**hint**: size, itemsize)"
    ]
   },
   {
@@ -85,7 +85,7 @@
    "metadata": {},
    "source": [
     "#### 5.  How to get the documentation of the numpy add function from the command line? (★☆☆) \n",
-    "##### (hint: np.info)"
+    "(**hint**: np.info)"
    ]
   },
   {
@@ -102,7 +102,7 @@
    "metadata": {},
    "source": [
     "#### 6.  Create a null vector of size 10 but the fifth value which is 1 (★☆☆) \n",
-    "##### (hint: array\\[4\\])"
+    "(**hint**: array\\[4\\])"
    ]
   },
   {
@@ -119,7 +119,7 @@
    "metadata": {},
    "source": [
     "#### 7.  Create a vector with values ranging from 10 to 49 (★☆☆) \n",
-    "##### (hint: np.arange)"
+    "(**hint**: np.arange)"
    ]
   },
   {
@@ -136,7 +136,7 @@
    "metadata": {},
    "source": [
     "#### 8.  Reverse a vector (first element becomes last) (★☆☆) \n",
-    "##### (hint: array\\[::-1\\])"
+    "(**hint**: array\\[::-1\\])"
    ]
   },
   {
@@ -153,7 +153,7 @@
    "metadata": {},
    "source": [
     "#### 9.  Create a 3x3 matrix with values ranging from 0 to 8 (★☆☆) \n",
-    "##### (hint: reshape)"
+    "(**hint**: reshape)"
    ]
   },
   {
@@ -170,7 +170,7 @@
    "metadata": {},
    "source": [
     "#### 10. Find indices of non-zero elements from \\[1,2,0,0,4,0\\] (★☆☆) \n",
-    "##### (hint: np.nonzero)"
+    "(**hint**: np.nonzero)"
    ]
   },
   {
@@ -187,7 +187,7 @@
    "metadata": {},
    "source": [
     "#### 11. Create a 3x3 identity matrix (★☆☆) \n",
-    "##### (hint: np.eye)"
+    "(**hint**: np.eye)"
    ]
   },
   {
@@ -204,7 +204,7 @@
    "metadata": {},
    "source": [
     "#### 12. Create a 3x3x3 array with random values (★☆☆) \n",
-    "##### (hint: np.random.random)"
+    "(**hint**: np.random.random)"
    ]
   },
   {
@@ -221,7 +221,7 @@
    "metadata": {},
    "source": [
     "#### 13. Create a 10x10 array with random values and find the minimum and maximum values (★☆☆) \n",
-    "##### (hint: min, max)"
+    "(**hint**: min, max)"
    ]
   },
   {
@@ -238,7 +238,7 @@
    "metadata": {},
    "source": [
     "#### 14. Create a random vector of size 30 and find the mean value (★☆☆) \n",
-    "##### (hint: mean)"
+    "(**hint**: mean)"
    ]
   },
   {
@@ -255,7 +255,7 @@
    "metadata": {},
    "source": [
     "#### 15. Create a 2d array with 1 on the border and 0 inside (★☆☆) \n",
-    "##### (hint: array\\[1:-1, 1:-1\\])"
+    "(**hint**: array\\[1:-1, 1:-1\\])"
    ]
   },
   {
@@ -272,7 +272,7 @@
    "metadata": {},
    "source": [
     "#### 16. How to add a border (filled with 0's) around an existing array? (★☆☆) \n",
-    "##### (hint: np.pad)"
+    "(**hint**: np.pad)"
    ]
   },
   {
@@ -289,7 +289,7 @@
    "metadata": {},
    "source": [
     "#### 17. What is the result of the following expression? (★☆☆) \n",
-    "##### (hint: NaN = not a number, inf = infinity)"
+    "(**hint**: NaN = not a number, inf = infinity)"
    ]
   },
   {
@@ -319,7 +319,7 @@
    "metadata": {},
    "source": [
     "#### 18. Create a 5x5 matrix with values 1,2,3,4 just below the diagonal (★☆☆) \n",
-    "##### (hint: np.diag)"
+    "(**hint**: np.diag)"
    ]
   },
   {
@@ -336,7 +336,7 @@
    "metadata": {},
    "source": [
     "#### 19. Create a 8x8 matrix and fill it with a checkerboard pattern (★☆☆) \n",
-    "##### (hint: array\\[::2\\])"
+    "(**hint**: array\\[::2\\])"
    ]
   },
   {
@@ -353,7 +353,7 @@
    "metadata": {},
    "source": [
     "#### 20. Consider a (6,7,8) shape array, what is the index (x,y,z) of the 100th element? \n",
-    "##### (hint: np.unravel_index)"
+    "(**hint**: np.unravel_index)"
    ]
   },
   {
@@ -370,7 +370,7 @@
    "metadata": {},
    "source": [
     "#### 21. Create a checkerboard 8x8 matrix using the tile function (★☆☆) \n",
-    "##### (hint: np.tile)"
+    "(**hint**: np.tile)"
    ]
   },
   {
@@ -387,7 +387,7 @@
    "metadata": {},
    "source": [
     "#### 22. Normalize a 5x5 random matrix (★☆☆) \n",
-    "##### (hint: (x - min) / (max - min))"
+    "(**hint**: (x - min) / (max - min))"
    ]
   },
   {
@@ -404,7 +404,7 @@
    "metadata": {},
    "source": [
     "#### 23. Create a custom dtype that describes a color as four unsigned bytes (RGBA) (★☆☆) \n",
-    "##### (hint: np.dtype)"
+    "(**hint**: np.dtype)"
    ]
   },
   {
@@ -421,7 +421,7 @@
    "metadata": {},
    "source": [
     "#### 24. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆) \n",
-    "##### (hint: np.dot | @)"
+    "(**hint**: np.dot | @)"
    ]
   },
   {
@@ -438,7 +438,7 @@
    "metadata": {},
    "source": [
     "#### 25. Given a 1D array, negate all elements which are between 3 and 8, in place. (★☆☆) \n",
-    "##### (hint: >, <=)"
+    "(**hint**: >, <=)"
    ]
   },
   {
@@ -455,7 +455,7 @@
    "metadata": {},
    "source": [
     "#### 26. What is the output of the following script? (★☆☆) \n",
-    "##### (hint: np.sum)"
+    "(**hint**: np.sum)"
    ]
   },
   {
@@ -542,7 +542,7 @@
    "metadata": {},
    "source": [
     "#### 29. How to round away from zero a float array ? (★☆☆) \n",
-    "##### (hint: np.uniform, np.copysign, np.ceil, np.abs)"
+    "(**hint**: np.uniform, np.copysign, np.ceil, np.abs)"
    ]
   },
   {
@@ -559,7 +559,7 @@
    "metadata": {},
    "source": [
     "#### 30. How to find common values between two arrays? (★☆☆) \n",
-    "##### (hint: np.intersect1d)"
+    "(**hint**: np.intersect1d)"
    ]
   },
   {
@@ -576,7 +576,7 @@
    "metadata": {},
    "source": [
     "#### 31. How to ignore all numpy warnings (not recommended)? (★☆☆) \n",
-    "##### (hint: np.seterr, np.errstate)"
+    "(**hint**: np.seterr, np.errstate)"
    ]
   },
   {
@@ -593,7 +593,7 @@
    "metadata": {},
    "source": [
     "#### 32. Is the following expressions true? (★☆☆) \n",
-    "##### (hint: imaginary number)"
+    "(**hint**: imaginary number)"
    ]
   },
   {
@@ -619,7 +619,7 @@
    "metadata": {},
    "source": [
     "#### 33. How to get the dates of yesterday, today and tomorrow? (★☆☆) \n",
-    "##### (hint: np.datetime64, np.timedelta64)"
+    "(**hint**: np.datetime64, np.timedelta64)"
    ]
   },
   {
@@ -636,7 +636,7 @@
    "metadata": {},
    "source": [
     "#### 34. How to get all the dates corresponding to the month of July 2016? (★★☆) \n",
-    "##### (hint: np.arange(dtype=datetime64\\['D'\\]))"
+    "(**hint**: np.arange(dtype=datetime64\\['D'\\]))"
    ]
   },
   {
@@ -653,7 +653,7 @@
    "metadata": {},
    "source": [
     "#### 35. How to compute ((A+B)\\*(-A/2)) in place (without copy)? (★★☆) \n",
-    "##### (hint: np.add(out=), np.negative(out=), np.multiply(out=), np.divide(out=))"
+    "(**hint**: np.add(out=), np.negative(out=), np.multiply(out=), np.divide(out=))"
    ]
   },
   {
@@ -670,7 +670,7 @@
    "metadata": {},
    "source": [
     "#### 36. Extract the integer part of a random array using 5 different methods (★★☆) \n",
-    "##### (hint: %, np.floor, np.ceil, astype, np.trunc)"
+    "(**hint**: %, np.floor, np.ceil, astype, np.trunc)"
    ]
   },
   {
@@ -687,7 +687,7 @@
    "metadata": {},
    "source": [
     "#### 37. Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆) \n",
-    "##### (hint: np.arange)"
+    "(**hint**: np.arange)"
    ]
   },
   {
@@ -704,7 +704,7 @@
    "metadata": {},
    "source": [
     "#### 38. Consider a generator function that generates 10 integers and use it to build an array (★☆☆) \n",
-    "##### (hint: np.fromiter)"
+    "(**hint**: np.fromiter)"
    ]
   },
   {
@@ -721,7 +721,7 @@
    "metadata": {},
    "source": [
     "#### 39. Create a vector of size 10 with values ranging from 0 to 1, both excluded (★★☆) \n",
-    "##### (hint: np.linespace)"
+    "(**hint**: np.linespace)"
    ]
   },
   {
@@ -738,7 +738,7 @@
    "metadata": {},
    "source": [
     "#### 40. Create a random vector of size 10 and sort it (★★☆) \n",
-    "##### (hint: sort)"
+    "(**hint**: sort)"
    ]
   },
   {
@@ -755,7 +755,7 @@
    "metadata": {},
    "source": [
     "#### 41. How to sum a small array faster than np.sum? (★★☆) \n",
-    "##### (hint: np.add.reduce)"
+    "(**hint**: np.add.reduce)"
    ]
   },
   {
@@ -772,7 +772,7 @@
    "metadata": {},
    "source": [
     "#### 42. Consider two random array A and B, check if they are equal (★★☆) \n",
-    "##### (hint: np.allclose, np.array\\_equal)"
+    "(**hint**: np.allclose, np.array\\_equal)"
    ]
   },
   {
@@ -789,7 +789,7 @@
    "metadata": {},
    "source": [
     "#### 43. Make an array immutable (read-only) (★★☆) \n",
-    "##### (hint: flags.writeable)"
+    "(**hint**: flags.writeable)"
    ]
   },
   {
@@ -806,7 +806,7 @@
    "metadata": {},
    "source": [
     "#### 44. Consider a random 10x2 matrix representing cartesian coordinates, convert them to polar coordinates (★★☆) \n",
-    "##### (hint: np.sqrt, np.arctan2)"
+    "(**hint**: np.sqrt, np.arctan2)"
    ]
   },
   {
@@ -823,7 +823,7 @@
    "metadata": {},
    "source": [
     "#### 45. Create random vector of size 10 and replace the maximum value by 0 (★★☆) \n",
-    "##### (hint: argmax)"
+    "(**hint**: argmax)"
    ]
   },
   {
@@ -840,7 +840,7 @@
    "metadata": {},
    "source": [
     "#### 46. Create a structured array with `x` and `y` coordinates covering the \\[0,1\\]x\\[0,1\\] area (★★☆) \n",
-    "##### (hint: np.meshgrid)"
+    "(**hint**: np.meshgrid)"
    ]
   },
   {
@@ -857,7 +857,7 @@
    "metadata": {},
    "source": [
     "####  47. Given two arrays, X and Y, construct the Cauchy matrix C (Cij =1/(xi - yj)) \n",
-    "##### (hint: np.subtract.outer)"
+    "(**hint**: np.subtract.outer)"
    ]
   },
   {
@@ -874,7 +874,7 @@
    "metadata": {},
    "source": [
     "#### 48. Print the minimum and maximum representable value for each numpy scalar type (★★☆) \n",
-    "##### (hint: np.iinfo, np.finfo, eps)"
+    "(**hint**: np.iinfo, np.finfo, eps)"
    ]
   },
   {
@@ -891,7 +891,7 @@
    "metadata": {},
    "source": [
     "#### 49. How to print all the values of an array? (★★☆) \n",
-    "##### (hint: np.set\\_printoptions)"
+    "(**hint**: np.set\\_printoptions)"
    ]
   },
   {
@@ -908,7 +908,7 @@
    "metadata": {},
    "source": [
     "#### 50. How to find the closest value (to a given scalar) in a vector? (★★☆) \n",
-    "##### (hint: argmin)"
+    "(**hint**: argmin)"
    ]
   },
   {
@@ -925,7 +925,7 @@
    "metadata": {},
    "source": [
     "#### 51. Create a structured array representing a position (x,y) and a color (r,g,b) (★★☆) \n",
-    "##### (hint: dtype)"
+    "(**hint**: dtype)"
    ]
   },
   {
@@ -942,7 +942,7 @@
    "metadata": {},
    "source": [
     "#### 52. Consider a random vector with shape (100,2) representing coordinates, find point by point distances (★★☆) \n",
-    "##### (hint: np.atleast\\_2d, T, np.sqrt)"
+    "(**hint**: np.atleast\\_2d, T, np.sqrt)"
    ]
   },
   {
@@ -959,7 +959,7 @@
    "metadata": {},
    "source": [
     "#### 53. How to convert a float (32 bits) array into an integer (32 bits) in place? \n",
-    "##### (hint: astype(copy=False))"
+    "(**hint**: astype(copy=False))"
    ]
   },
   {
@@ -976,7 +976,7 @@
    "metadata": {},
    "source": [
     "#### 54. How to read the following file? (★★☆) \n",
-    "##### (hint: np.genfromtxt)"
+    "(**hint**: np.genfromtxt)"
    ]
   },
   {
@@ -1004,7 +1004,7 @@
    "metadata": {},
    "source": [
     "#### 55. What is the equivalent of enumerate for numpy arrays? (★★☆) \n",
-    "##### (hint: np.ndenumerate, np.ndindex)"
+    "(**hint**: np.ndenumerate, np.ndindex)"
    ]
   },
   {
@@ -1021,7 +1021,7 @@
    "metadata": {},
    "source": [
     "#### 56. Generate a generic 2D Gaussian-like array (★★☆) \n",
-    "##### (hint: np.meshgrid, np.exp)"
+    "(**hint**: np.meshgrid, np.exp)"
    ]
   },
   {
@@ -1038,7 +1038,7 @@
    "metadata": {},
    "source": [
     "#### 57. How to randomly place p elements in a 2D array? (★★☆) \n",
-    "##### (hint: np.put, np.random.choice)"
+    "(**hint**: np.put, np.random.choice)"
    ]
   },
   {
@@ -1055,7 +1055,7 @@
    "metadata": {},
    "source": [
     "#### 58. Subtract the mean of each row of a matrix (★★☆) \n",
-    "##### (hint: mean(axis=,keepdims=))"
+    "(**hint**: mean(axis=,keepdims=))"
    ]
   },
   {
@@ -1072,7 +1072,7 @@
    "metadata": {},
    "source": [
     "#### 59. How to sort an array by the nth column? (★★☆) \n",
-    "##### (hint: argsort)"
+    "(**hint**: argsort)"
    ]
   },
   {
@@ -1089,7 +1089,7 @@
    "metadata": {},
    "source": [
     "#### 60. How to tell if a given 2D array has null columns? (★★☆) \n",
-    "##### (hint: any, ~)"
+    "(**hint**: any, ~)"
    ]
   },
   {
@@ -1106,7 +1106,7 @@
    "metadata": {},
    "source": [
     "#### 61. Find the nearest value from a given value in an array (★★☆) \n",
-    "##### (hint: np.abs, argmin, flat)"
+    "(**hint**: np.abs, argmin, flat)"
    ]
   },
   {
@@ -1123,7 +1123,7 @@
    "metadata": {},
    "source": [
     "#### 62. Considering two arrays with shape (1,3) and (3,1), how to compute their sum using an iterator? (★★☆) \n",
-    "##### (hint: np.nditer)"
+    "(**hint**: np.nditer)"
    ]
   },
   {
@@ -1140,7 +1140,7 @@
    "metadata": {},
    "source": [
     "#### 63. Create an array class that has a name attribute (★★☆) \n",
-    "##### (hint: class method)"
+    "(**hint**: class method)"
    ]
   },
   {
@@ -1157,7 +1157,7 @@
    "metadata": {},
    "source": [
     "#### 64. Consider a given vector, how to add 1 to each element indexed by a second vector (be careful with repeated indices)? (★★★) \n",
-    "##### (hint: np.bincount | np.add.at)"
+    "(**hint**: np.bincount | np.add.at)"
    ]
   },
   {
@@ -1174,7 +1174,7 @@
    "metadata": {},
    "source": [
     "#### 65. How to accumulate elements of a vector (X) to an array (F) based on an index list (I)? (★★★) \n",
-    "##### (hint: np.bincount)"
+    "(**hint**: np.bincount)"
    ]
   },
   {
@@ -1191,7 +1191,7 @@
    "metadata": {},
    "source": [
     "#### 66. Considering a (w,h,3) image of (dtype=ubyte), compute the number of unique colors (★★★) \n",
-    "##### (hint: np.unique)"
+    "(**hint**: np.unique)"
    ]
   },
   {
@@ -1208,7 +1208,7 @@
    "metadata": {},
    "source": [
     "#### 67. Considering a four dimensions array, how to get sum over the last two axis at once? (★★★) \n",
-    "##### (hint: sum(axis=(-2,-1)))"
+    "(**hint**: sum(axis=(-2,-1)))"
    ]
   },
   {
@@ -1225,7 +1225,7 @@
    "metadata": {},
    "source": [
     "#### 68. Considering a one-dimensional vector D, how to compute means of subsets of D using a vector S of same size describing subset  indices? (★★★) \n",
-    "##### (hint: np.bincount)"
+    "(**hint**: np.bincount)"
    ]
   },
   {
@@ -1242,7 +1242,7 @@
    "metadata": {},
    "source": [
     "#### 69. How to get the diagonal of a dot product? (★★★) \n",
-    "##### (hint: np.diag)"
+    "(**hint**: np.diag)"
    ]
   },
   {
@@ -1259,7 +1259,7 @@
    "metadata": {},
    "source": [
     "#### 70. Consider the vector \\[1, 2, 3, 4, 5\\], how to build a new vector with 3 consecutive zeros interleaved between each value? (★★★) \n",
-    "##### (hint: array\\[::4\\])"
+    "(**hint**: array\\[::4\\])"
    ]
   },
   {
@@ -1276,7 +1276,7 @@
    "metadata": {},
    "source": [
     "#### 71. Consider an array of dimension (5,5,3), how to mulitply it by an array with dimensions (5,5)? (★★★) \n",
-    "##### (hint: array\\[:, :, None\\])"
+    "(**hint**: array\\[:, :, None\\])"
    ]
   },
   {
@@ -1293,7 +1293,7 @@
    "metadata": {},
    "source": [
     "#### 72. How to swap two rows of an array? (★★★) \n",
-    "##### (hint: array\\[\\[\\]\\] = array\\[\\[\\]\\])"
+    "(**hint**: array\\[\\[\\]\\] = array\\[\\[\\]\\])"
    ]
   },
   {
@@ -1310,7 +1310,7 @@
    "metadata": {},
    "source": [
     "#### 73. Consider a set of 10 triplets describing 10 triangles (with shared vertices), find the set of unique line segments composing all the  triangles (★★★) \n",
-    "##### (hint: repeat, np.roll, np.sort, view, np.unique)"
+    "(**hint**: repeat, np.roll, np.sort, view, np.unique)"
    ]
   },
   {
@@ -1327,7 +1327,7 @@
    "metadata": {},
    "source": [
     "#### 74. Given an array C that is a bincount, how to produce an array A such that np.bincount(A) == C? (★★★) \n",
-    "##### (hint: np.repeat)"
+    "(**hint**: np.repeat)"
    ]
   },
   {
@@ -1344,7 +1344,7 @@
    "metadata": {},
    "source": [
     "#### 75. How to compute averages using a sliding window over an array? (★★★) \n",
-    "##### (hint: np.cumsum)"
+    "(**hint**: np.cumsum)"
    ]
   },
   {
@@ -1361,7 +1361,7 @@
    "metadata": {},
    "source": [
     "#### 76. Consider a one-dimensional array Z, build a two-dimensional array whose first row is (Z\\[0\\],Z\\[1\\],Z\\[2\\]) and each subsequent row is  shifted by 1 (last row should be (Z\\[-3\\],Z\\[-2\\],Z\\[-1\\]) (★★★) \n",
-    "##### (hint: from numpy.lib import stride_tricks)"
+    "(**hint**: from numpy.lib import stride_tricks)"
    ]
   },
   {
@@ -1378,7 +1378,7 @@
    "metadata": {},
    "source": [
     "#### 77. How to negate a boolean, or to change the sign of a float inplace? (★★★) \n",
-    "##### (hint: np.logical_not, np.negative)"
+    "(**hint**: np.logical_not, np.negative)"
    ]
   },
   {
@@ -1427,7 +1427,7 @@
    "metadata": {},
    "source": [
     "#### 80. Consider an arbitrary array, write a function that extract a subpart with a fixed shape and centered on a given element (pad with a `fill` value when necessary) (★★★) \n",
-    "##### (hint: minimum, maximum)"
+    "(**hint**: minimum, maximum)"
    ]
   },
   {
@@ -1444,7 +1444,7 @@
    "metadata": {},
    "source": [
     "#### 81. Consider an array Z = \\[1,2,3,4,5,6,7,8,9,10,11,12,13,14\\], how to generate an array R = \\[\\[1,2,3,4\\], \\[2,3,4,5\\], \\[3,4,5,6\\], ..., \\[11,12,13,14\\]\\]? (★★★) \n",
-    "##### (hint: stride\\_tricks.as\\_strided)"
+    "(**hint**: stride\\_tricks.as\\_strided)"
    ]
   },
   {
@@ -1461,7 +1461,7 @@
    "metadata": {},
    "source": [
     "#### 82. Compute a matrix rank (★★★) \n",
-    "##### (hint: np.linalg.svd) (suggestion: np.linalg.svd)"
+    "(**hint**: np.linalg.svd) (suggestion: np.linalg.svd)"
    ]
   },
   {
@@ -1478,7 +1478,7 @@
    "metadata": {},
    "source": [
     "#### 83. How to find the most frequent value in an array? \n",
-    "##### (hint: np.bincount, argmax)"
+    "(**hint**: np.bincount, argmax)"
    ]
   },
   {
@@ -1495,7 +1495,7 @@
    "metadata": {},
    "source": [
     "#### 84. Extract all the contiguous 3x3 blocks from a random 10x10 matrix (★★★) \n",
-    "##### (hint: stride\\_tricks.as\\_strided)"
+    "(**hint**: stride\\_tricks.as\\_strided)"
    ]
   },
   {
@@ -1512,7 +1512,7 @@
    "metadata": {},
    "source": [
     "#### 85. Create a 2D array subclass such that Z\\[i,j\\] == Z\\[j,i\\] (★★★) \n",
-    "##### (hint: class method)"
+    "(**hint**: class method)"
    ]
   },
   {
@@ -1529,7 +1529,7 @@
    "metadata": {},
    "source": [
     "#### 86. Consider a set of p matrices wich shape (n,n) and a set of p vectors with shape (n,1). How to compute the sum of of the p matrix products at once? (result has shape (n,1)) (★★★) \n",
-    "##### (hint: np.tensordot)"
+    "(**hint**: np.tensordot)"
    ]
   },
   {
@@ -1546,7 +1546,7 @@
    "metadata": {},
    "source": [
     "#### 87. Consider a 16x16 array, how to get the block-sum (block size is 4x4)? (★★★) \n",
-    "##### (hint: np.add.reduceat)"
+    "(**hint**: np.add.reduceat)"
    ]
   },
   {
@@ -1579,7 +1579,7 @@
    "metadata": {},
    "source": [
     "#### 89. How to get the n largest values of an array (★★★) \n",
-    "##### (hint: np.argsort | np.argpartition)"
+    "(**hint**: np.argsort | np.argpartition)"
    ]
   },
   {
@@ -1596,7 +1596,7 @@
    "metadata": {},
    "source": [
     "#### 90. Given an arbitrary number of vectors, build the cartesian product (every combinations of every item) (★★★) \n",
-    "##### (hint: np.indices)"
+    "(**hint**: np.indices)"
    ]
   },
   {
@@ -1614,7 +1614,7 @@
    "metadata": {},
    "source": [
     "#### 91. How to create a record array from a regular array? (★★★) \n",
-    "##### (hint: np.core.records.fromarrays)"
+    "(**hint**: np.core.records.fromarrays)"
    ]
   },
   {
@@ -1631,7 +1631,7 @@
    "metadata": {},
    "source": [
     "#### 92. Consider a large vector Z, compute Z to the power of 3 using 3 different methods (★★★) \n",
-    "##### (hint: np.power, \\*, np.einsum)"
+    "(**hint**: np.power, \\*, np.einsum)"
    ]
   },
   {
@@ -1648,7 +1648,7 @@
    "metadata": {},
    "source": [
     "#### 93. Consider two arrays A and B of shape (8,3) and (2,2). How to find rows of A that contain elements of each row of B regardless of the order of the elements in B? (★★★) \n",
-    "##### (hint: np.where)"
+    "(**hint**: np.where)"
    ]
   },
   {
@@ -1681,7 +1681,7 @@
    "metadata": {},
    "source": [
     "#### 95. Convert a vector of ints into a matrix binary representation (★★★) \n",
-    "##### (hint: np.unpackbits)"
+    "(**hint**: np.unpackbits)"
    ]
   },
   {
@@ -1698,7 +1698,7 @@
    "metadata": {},
    "source": [
     "#### 96. Given a two dimensional array, how to extract unique rows? (★★★) \n",
-    "##### (hint: np.ascontiguousarray)"
+    "(**hint**: np.ascontiguousarray)"
    ]
   },
   {
@@ -1715,7 +1715,7 @@
    "metadata": {},
    "source": [
     "#### 97. Considering 2 vectors A & B, write the einsum equivalent of inner, outer, sum, and mul function (★★★) \n",
-    "##### (hint: np.einsum)"
+    "(**hint**: np.einsum)"
    ]
   },
   {
@@ -1732,7 +1732,7 @@
    "metadata": {},
    "source": [
     "#### 98. Considering a path described by two vectors (X,Y), how to sample it using equidistant samples (★★★)? \n",
-    "##### (hint: np.cumsum, np.interp)"
+    "(**hint**: np.cumsum, np.interp)"
    ]
   },
   {
@@ -1749,7 +1749,7 @@
    "metadata": {},
    "source": [
     "#### 99. Given an integer n and a 2D array X, select from X the rows which can be interpreted as draws from a multinomial distribution with n degrees, i.e., the rows which only contain integers and which sum to n. (★★★) \n",
-    "##### (hint: np.logical\\_and.reduce, np.mod)"
+    "(**hint**: np.logical\\_and.reduce, np.mod)"
    ]
   },
   {
@@ -1766,7 +1766,7 @@
    "metadata": {},
    "source": [
     "#### 100. Compute bootstrapped 95% confidence intervals for the mean of a 1D array X (i.e., resample the elements of an array with replacement N times, compute the mean of each sample, and then compute percentiles over the means). (★★★) \n",
-    "##### (hint: np.percentile)"
+    "(**hint**: np.percentile)"
    ]
   },
   {
diff --git a/100 Numpy exercises with hint.md b/100 Numpy exercises with hint.md
index 3c10d89..cd92748 100644
--- a/100 Numpy exercises with hint.md	
+++ b/100 Numpy exercises with hint.md	
@@ -12,103 +12,103 @@ free to open an issue at <https://github.com/rougier/numpy-100>
 
 #### 1. Import the numpy package under the name `np` (★☆☆) 
 
-##### (hint: import … as ..)
+(**hint**: import … as ..)
 
 
 
 #### 2. Print the numpy version and the configuration (★☆☆) 
 
-##### (hint: np.\_\_verison\_\_, np.show\_config)
+(**hint**: np.\_\_verison\_\_, np.show\_config)
 
 
 
 #### 3. Create a null vector of size 10 (★☆☆) 
 
-##### (hint: np.zeros)
+(**hint**: np.zeros)
 
 
 
 #### 4.  How to find the memory size of any array (★☆☆) 
 
-##### (hint: size, itemsize)
+(**hint**: size, itemsize)
 
 
 
 #### 5.  How to get the documentation of the numpy add function from the command line? (★☆☆) 
 
-##### (hint: np.info)
+(**hint**: np.info)
 
 
 
 #### 6.  Create a null vector of size 10 but the fifth value which is 1 (★☆☆) 
 
-##### (hint: array\[4\])
+(**hint**: array\[4\])
 
 
 
 #### 7.  Create a vector with values ranging from 10 to 49 (★☆☆) 
 
-##### (hint: np.arange)
+(**hint**: np.arange)
 
 
 
 #### 8.  Reverse a vector (first element becomes last) (★☆☆) 
 
-##### (hint: array\[::-1\])
+(**hint**: array\[::-1\])
 
 
 
 #### 9.  Create a 3x3 matrix with values ranging from 0 to 8 (★☆☆) 
 
-##### (hint: reshape)
+(**hint**: reshape)
 
 
 
 #### 10. Find indices of non-zero elements from \[1,2,0,0,4,0\] (★☆☆) 
 
-##### (hint: np.nonzero)
+(**hint**: np.nonzero)
 
 
 
 #### 11. Create a 3x3 identity matrix (★☆☆) 
 
-##### (hint: np.eye)
+(**hint**: np.eye)
 
 
 
 #### 12. Create a 3x3x3 array with random values (★☆☆) 
 
-##### (hint: np.random.random)
+(**hint**: np.random.random)
 
 
 
 #### 13. Create a 10x10 array with random values and find the minimum and maximum values (★☆☆) 
 
-##### (hint: min, max)
+(**hint**: min, max)
 
 
 
 #### 14. Create a random vector of size 30 and find the mean value (★☆☆) 
 
-##### (hint: mean)
+(**hint**: mean)
 
 
 
 #### 15. Create a 2d array with 1 on the border and 0 inside (★☆☆) 
 
-##### (hint: array\[1:-1, 1:-1\])
+(**hint**: array\[1:-1, 1:-1\])
 
 
 
 #### 16. How to add a border (filled with 0's) around an existing array? (★☆☆) 
 
-##### (hint: np.pad)
+(**hint**: np.pad)
 
 
 
 #### 17. What is the result of the following expression? (★☆☆) 
 
-##### (hint: NaN = not a number, inf = infinity)
+(**hint**: NaN = not a number, inf = infinity)
 
 
 ```python
@@ -121,55 +121,55 @@ np.nan - np.nan
 
 #### 18. Create a 5x5 matrix with values 1,2,3,4 just below the diagonal (★☆☆) 
 
-##### (hint: np.diag)
+(**hint**: np.diag)
 
 
 
 #### 19. Create a 8x8 matrix and fill it with a checkerboard pattern (★☆☆) 
 
-##### (hint: array\[::2\])
+(**hint**: array\[::2\])
 
 
 
 #### 20. Consider a (6,7,8) shape array, what is the index (x,y,z) of the 100th element? 
 
-##### (hint: np.unravel\_index)
+(**hint**: np.unravel\_index)
 
 
 
 #### 21. Create a checkerboard 8x8 matrix using the tile function (★☆☆) 
 
-##### (hint: np.tile)
+(**hint**: np.tile)
 
 
 
 #### 22. Normalize a 5x5 random matrix (★☆☆) 
 
-##### (hint: (x - min) / (max - min))
+(**hint**: (x - min) / (max - min))
 
 
 
 #### 23. Create a custom dtype that describes a color as four unsigned bytes (RGBA) (★☆☆) 
 
-##### (hint: np.dtype)
+(**hint**: np.dtype)
 
 
 
 #### 24. Multiply a 5x3 matrix by a 3x2 matrix (real matrix product) (★☆☆) 
 
-##### (hint: np.dot | @)
+(**hint**: np.dot | @)
 
 
 
 #### 25. Given a 1D array, negate all elements which are between 3 and 8, in place. (★☆☆) 
 
-##### (hint: >, <=)
+(**hint**: >, <=)
 
 
 
 #### 26. What is the output of the following script? (★☆☆) 
 
-##### (hint: np.sum)
+(**hint**: np.sum)
 
 
 ```python
@@ -203,25 +203,25 @@ np.array([np.nan]).astype(int).astype(float)
 
 #### 29. How to round away from zero a float array ? (★☆☆) 
 
-##### (hint: np.uniform, np.copysign, np.ceil, np.abs)
+(**hint**: np.uniform, np.copysign, np.ceil, np.abs)
 
 
 
 #### 30. How to find common values between two arrays? (★☆☆) 
 
-##### (hint: np.intersect1d)
+(**hint**: np.intersect1d)
 
 
 
 #### 31. How to ignore all numpy warnings (not recommended)? (★☆☆) 
 
-##### (hint: np.seterr, np.errstate)
+(**hint**: np.seterr, np.errstate)
 
 
 
 #### 32. Is the following expressions true? (★☆☆) 
 
-##### (hint: imaginary number)
+(**hint**: imaginary number)
 
 
 ```python
@@ -230,85 +230,85 @@ np.sqrt(-1) == np.emath.sqrt(-1)
 
 #### 33. How to get the dates of yesterday, today and tomorrow? (★☆☆) 
 
-##### (hint: np.datetime64, np.timedelta64)
+(**hint**: np.datetime64, np.timedelta64)
 
 
 
 #### 34. How to get all the dates corresponding to the month of July 2016? (★★☆) 
 
-##### (hint: np.arange(dtype=datetime64\['D'\]))
+(**hint**: np.arange(dtype=datetime64\['D'\]))
 
 
 
 #### 35. How to compute ((A+B)\*(-A/2)) in place (without copy)? (★★☆) 
 
-##### (hint: np.add(out=), np.negative(out=), np.multiply(out=), np.divide(out=))
+(**hint**: np.add(out=), np.negative(out=), np.multiply(out=), np.divide(out=))
 
 
 
 #### 36. Extract the integer part of a random array using 5 different methods (★★☆) 
 
-##### (hint: %, np.floor, np.ceil, astype, np.trunc)
+(**hint**: %, np.floor, np.ceil, astype, np.trunc)
 
 
 
 #### 37. Create a 5x5 matrix with row values ranging from 0 to 4 (★★☆) 
 
-##### (hint: np.arange)
+(**hint**: np.arange)
 
 
 
 #### 38. Consider a generator function that generates 10 integers and use it to build an array (★☆☆) 
 
-##### (hint: np.fromiter)
+(**hint**: np.fromiter)
 
 
 
 #### 39. Create a vector of size 10 with values ranging from 0 to 1, both excluded (★★☆) 
 
-##### (hint: np.linespace)
+(**hint**: np.linespace)
 
 
 
 #### 40. Create a random vector of size 10 and sort it (★★☆) 
 
-##### (hint: sort)
+(**hint**: sort)
 
 
 
 #### 41. How to sum a small array faster than np.sum? (★★☆) 
 
-##### (hint: np.add.reduce)
+(**hint**: np.add.reduce)
 
 
 
 #### 42. Consider two random array A and B, check if they are equal (★★☆) 
 
-##### (hint: np.allclose, np.array\_equal)
+(**hint**: np.allclose, np.array\_equal)
 
 
 
 #### 43. Make an array immutable (read-only) (★★☆) 
 
-##### (hint: flags.writeable)
+(**hint**: flags.writeable)
 
 
 
 #### 44. Consider a random 10x2 matrix representing cartesian coordinates, convert them to polar coordinates (★★☆) 
 
-##### (hint: np.sqrt, np.arctan2)
+(**hint**: np.sqrt, np.arctan2)
 
 
 
 #### 45. Create random vector of size 10 and replace the maximum value by 0 (★★☆) 
 
-##### (hint: argmax)
+(**hint**: argmax)
 
 
 
 #### 46. Create a structured array with `x` and `y` coordinates covering the \[0,1\]x\[0,1\] area (★★☆) 
 
-##### (hint: np.meshgrid)
+(**hint**: np.meshgrid)
 
 
 
@@ -320,43 +320,43 @@ np.sqrt(-1) == np.emath.sqrt(-1)
 
 #### 48. Print the minimum and maximum representable value for each numpy scalar type (★★☆) 
 
-##### (hint: np.iinfo, np.finfo, eps)
+(**hint**: np.iinfo, np.finfo, eps)
 
 
 
 #### 49. How to print all the values of an array? (★★☆) 
 
-##### (hint: np.set\_printoptions)
+(**hint**: np.set\_printoptions)
 
 
 
 #### 50. How to find the closest value (to a given scalar) in a vector? (★★☆) 
 
-##### (hint: argmin)
+(**hint**: argmin)
 
 
 
 #### 51. Create a structured array representing a position (x,y) and a color (r,g,b) (★★☆) 
 
-##### (hint: dtype)
+(**hint**: dtype)
 
 
 
 #### 52. Consider a random vector with shape (100,2) representing coordinates, find point by point distances (★★☆) 
 
-##### (hint: np.atleast\_2d, T, np.sqrt)
+(**hint**: np.atleast\_2d, T, np.sqrt)
 
 
 
 #### 53. How to convert a float (32 bits) array into an integer (32 bits) in place? 
 
-##### (hint: astype(copy=False))
+(**hint**: astype(copy=False))
 
 
 
 #### 54. How to read the following file? (★★☆) 
 
-##### (hint: np.genfromtxt)
+(**hint**: np.genfromtxt)
 
 
 ```
@@ -367,139 +367,139 @@ np.sqrt(-1) == np.emath.sqrt(-1)
 
 #### 55. What is the equivalent of enumerate for numpy arrays? (★★☆) 
 
-##### (hint: np.ndenumerate, np.ndindex)
+(**hint**: np.ndenumerate, np.ndindex)
 
 
 
 #### 56. Generate a generic 2D Gaussian-like array (★★☆) 
 
-##### (hint: np.meshgrid, np.exp)
+(**hint**: np.meshgrid, np.exp)
 
 
 
 #### 57. How to randomly place p elements in a 2D array? (★★☆) 
 
-##### (hint: np.put, np.random.choice)
+(**hint**: np.put, np.random.choice)
 
 
 
 #### 58. Subtract the mean of each row of a matrix (★★☆) 
 
-##### (hint: mean(axis=,keepdims=))
+(**hint**: mean(axis=,keepdims=))
 
 
 
 #### 59. How to sort an array by the nth column? (★★☆) 
 
-##### (hint: argsort)
+(**hint**: argsort)
 
 
 
 #### 60. How to tell if a given 2D array has null columns? (★★☆) 
 
-##### (hint: any, ~)
+(**hint**: any, ~)
 
 
 
 #### 61. Find the nearest value from a given value in an array (★★☆) 
 
-##### (hint: np.abs, argmin, flat)
+(**hint**: np.abs, argmin, flat)
 
 
 
 #### 62. Considering two arrays with shape (1,3) and (3,1), how to compute their sum using an iterator? (★★☆) 
 
-##### (hint: np.nditer)
+(**hint**: np.nditer)
 
 
 
 #### 63. Create an array class that has a name attribute (★★☆) 
 
-##### (hint: class method)
+(**hint**: class method)
 
 
 
 #### 64. Consider a given vector, how to add 1 to each element indexed by a second vector (be careful with repeated indices)? (★★★) 
 
-##### (hint: np.bincount | np.add.at)
+(**hint**: np.bincount | np.add.at)
 
 
 
 #### 65. How to accumulate elements of a vector (X) to an array (F) based on an index list (I)? (★★★) 
 
-##### (hint: np.bincount)
+(**hint**: np.bincount)
 
 
 
 #### 66. Considering a (w,h,3) image of (dtype=ubyte), compute the number of unique colors (★★★) 
 
-##### (hint: np.unique)
+(**hint**: np.unique)
 
 
 
 #### 67. Considering a four dimensions array, how to get sum over the last two axis at once? (★★★) 
 
-##### (hint: sum(axis=(-2,-1)))
+(**hint**: sum(axis=(-2,-1)))
 
 
 
 #### 68. Considering a one-dimensional vector D, how to compute means of subsets of D using a vector S of same size describing subset  indices? (★★★) 
 
-##### (hint: np.bincount)
+(**hint**: np.bincount)
 
 
 
 #### 69. How to get the diagonal of a dot product? (★★★) 
 
-##### (hint: np.diag)
+(**hint**: np.diag)
 
 
 
 #### 70. Consider the vector \[1, 2, 3, 4, 5\], how to build a new vector with 3 consecutive zeros interleaved between each value? (★★★) 
 
-##### (hint: array\[::4\])
+(**hint**: array\[::4\])
 
 
 
 #### 71. Consider an array of dimension (5,5,3), how to mulitply it by an array with dimensions (5,5)? (★★★) 
 
-##### (hint: array\[:, :, None\])
+(**hint**: array\[:, :, None\])
 
 
 
 #### 72. How to swap two rows of an array? (★★★) 
 
-##### (hint: array\[\[\]\] = array\[\[\]\])
+(**hint**: array\[\[\]\] = array\[\[\]\])
 
 
 
 #### 73. Consider a set of 10 triplets describing 10 triangles (with shared vertices), find the set of unique line segments composing all the  triangles (★★★) 
 
-##### (hint: repeat, np.roll, np.sort, view, np.unique)
+(**hint**: repeat, np.roll, np.sort, view, np.unique)
 
 
 
 #### 74. Given an array C that is a bincount, how to produce an array A such that np.bincount(A) == C? (★★★) 
 
-##### (hint: np.repeat)
+(**hint**: np.repeat)
 
 
 
 #### 75. How to compute averages using a sliding window over an array? (★★★) 
 
-##### (hint: np.cumsum)
+(**hint**: np.cumsum)
 
 
 
 #### 76. Consider a one-dimensional array Z, build a two-dimensional array whose first row is (Z\[0\],Z\[1\],Z\[2\]) and each subsequent row is  shifted by 1 (last row should be (Z\[-3\],Z\[-2\],Z\[-1\]) (★★★) 
 
-##### (hint: from numpy.lib import stride\_tricks)
+(**hint**: from numpy.lib import stride\_tricks)
 
 
 
 #### 77. How to negate a boolean, or to change the sign of a float inplace? (★★★) 
 
-##### (hint: np.logical_not, np.negative)
+(**hint**: np.logical_not, np.negative)
 
 
 
@@ -513,49 +513,49 @@ np.sqrt(-1) == np.emath.sqrt(-1)
 
 #### 80. Consider an arbitrary array, write a function that extract a subpart with a fixed shape and centered on a given element (pad with a `fill` value when necessary) (★★★) 
 
-##### (hint: minimum, maximum)
+(**hint**: minimum, maximum)
 
 
 
 #### 81. Consider an array Z = \[1,2,3,4,5,6,7,8,9,10,11,12,13,14\], how to generate an array R = \[\[1,2,3,4\], \[2,3,4,5\], \[3,4,5,6\], ..., \[11,12,13,14\]\]? (★★★) 
 
-##### (hint: stride\_tricks.as\_strided)
+(**hint**: stride\_tricks.as\_strided)
 
 
 
 #### 82. Compute a matrix rank (★★★) 
 
-##### (hint: np.linalg.svd)
+(**hint**: np.linalg.svd)
 
 
 
 #### 83. How to find the most frequent value in an array? 
 
-##### (hint: np.bincount, argmax)
+(**hint**: np.bincount, argmax)
 
 
 
 #### 84. Extract all the contiguous 3x3 blocks from a random 10x10 matrix (★★★) 
 
-##### (hint: stride\_tricks.as\_strided)
+(**hint**: stride\_tricks.as\_strided)
 
 
 
 #### 85. Create a 2D array subclass such that Z\[i,j\] == Z\[j,i\] (★★★) 
 
-##### (hint: class method)
+(**hint**: class method)
 
 
 
 #### 86. Consider a set of p matrices wich shape (n,n) and a set of p vectors with shape (n,1). How to compute the sum of of the p matrix products at once? (result has shape (n,1)) (★★★) 
 
-##### (hint: np.tensordot)
+(**hint**: np.tensordot)
 
 
 
 #### 87. Consider a 16x16 array, how to get the block-sum (block size is 4x4)? (★★★) 
 
-##### (hint: np.add.reduceat)
+(**hint**: np.add.reduceat)
 
 
 
@@ -565,31 +565,31 @@ np.sqrt(-1) == np.emath.sqrt(-1)
 
 #### 89. How to get the n largest values of an array (★★★) 
 
-##### (hint: np.argsort | np.argpartition)
+(**hint**: np.argsort | np.argpartition)
 
 
 
 #### 90. Given an arbitrary number of vectors, build the cartesian product (every combinations of every item) (★★★) 
 
-##### (hint: np.indices)
+(**hint**: np.indices)
 
 
 
 #### 91. How to create a record array from a regular array? (★★★) 
 
-##### (hint: np.core.records.fromarrays)
+(**hint**: np.core.records.fromarrays)
 
 
 
 #### 92. Consider a large vector Z, compute Z to the power of 3 using 3 different methods (★★★) 
 
-##### (hint: np.power, \*, np.einsum)
+(**hint**: np.power, \*, np.einsum)
 
 
 
 #### 93. Consider two arrays A and B of shape (8,3) and (2,2). How to find rows of A that contain elements of each row of B regardless of the order of the elements in B? (★★★) 
 
-##### (hint: np.where)
+(**hint**: np.where)
 
 
 
@@ -599,35 +599,35 @@ np.sqrt(-1) == np.emath.sqrt(-1)
 
 #### 95. Convert a vector of ints into a matrix binary representation (★★★) 
 
-##### (hint: np.unpackbits)
+(**hint**: np.unpackbits)
 
 
 
 #### 96. Given a two dimensional array, how to extract unique rows? (★★★) 
 
-##### (hint: np.ascontiguousarray)
+(**hint**: np.ascontiguousarray)
 
 
 
 #### 97. Considering 2 vectors A & B, write the einsum equivalent of inner, outer, sum, and mul function (★★★) 
 
-##### (hint: np.einsum)
+(**hint**: np.einsum)
 
 
 
 #### 98. Considering a path described by two vectors (X,Y), how to sample it using equidistant samples (★★★)? 
 
-##### (hint: np.cumsum, np.interp)
+(**hint**: np.cumsum, np.interp)
 
 
 
 #### 99. Given an integer n and a 2D array X, select from X the rows which can be interpreted as draws from a multinomial distribution with n degrees, i.e., the rows which only contain integers and which sum to n. (★★★) 
 
-##### (hint: np.logical\_and.reduce, np.mod)
+(**hint**: np.logical\_and.reduce, np.mod)
 
 
 
 #### 100. Compute bootstrapped 95% confidence intervals for the mean of a 1D array X (i.e., resample the elements of an array with replacement N times, compute the mean of each sample, and then compute percentiles over the means). (★★★) 
 
-##### (hint: np.percentile)
+(**hint**: np.percentile)