Solution to problem 10 in Python

src/Year_2018/P10.py

@@ -164,6 +164,7 @@
 import re
 from operator import itemgetter
 
+import matplotlib.pyplot as plt
 import numpy as np
 
 with open("files/P10.txt") as f:
@@ -179,8 +180,8 @@ def is_complete_row(line):
 
 def find_time(arr):
     # get position and velocity arrays
-    pos = arr[:, :2]
-    vel = arr[:, 2:]
+    pos = arr[:, :2].copy()
+    vel = arr[:, 2:].copy()
 
     found = False
     cnt = 0
@@ -193,3 +194,39 @@ def find_time(arr):
 
 
 message_time = find_time(points_arr)
+
+
+def find_message(arr, time):
+    pos = arr[:, :2].copy()
+    vel = arr[:, 2:].copy()
+
+    # get position when everything is lined up
+    pos += time * vel
+
+    # create canvas full of zeros big enough
+    # add one pixel to avoid IndexError when adding one during next step
+    canvas = np.zeros(pos.max(axis=0) + 1, dtype=np.int8)  # (194, 132)
+
+    # mark aligned pixels in the canvas by adding 1
+    canvas[pos[:, 0], pos[:, 1]] += 1
+
+    # show only pixels in canvas from the minimum of pos array
+    # this will show only the word
+    minx, miny = pos.min(axis=0)  # 132, 122
+    plt.imshow(canvas[minx:, miny:].T)
+    plt.show()
+
+
+find_message(arr=points_arr, time=message_time)
+
+
+# --- Part Two ---
+
+# Good thing you didn't have to wait, because that would have taken a long
+# time - much longer than the 3 seconds in the example above.
+
+# Impressed by your sub-hour communication capabilities, the Elves are curious:
+# exactly how many seconds would they have needed to wait for that message to
+# appear?
+
+print(f"Message appear at {message_time} s")