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Merge pull request #145 from MarkSetchell/Q66-Setchell

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Updated question 66
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Nicolas P. Rougier 2021-03-29 07:36:22 +02:00 committed by GitHub
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source/exercises100.ktx
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@ -864,11 +864,25 @@ hint: np.unique
# Author: Fisher Wang
w, h = 256, 256
I = np.random.randint(0, 4, (w, h, 3)).astype(np.ubyte)
I = np.random.randint(0, 4, (h, w, 3)).astype(np.ubyte)
colors = np.unique(I.reshape(-1, 3), axis=0)
n = len(colors)
print(n)
# Faster version
# Author: Mark Setchell
# https://stackoverflow.com/a/59671950/2836621
w, h = 256, 256
I = np.random.randint(0,4,(h,w,3), dtype=np.uint8)
# View each pixel as a single 24-bit integer, rather than three 8-bit bytes
I24 = np.dot(I.astype(np.uint32),[1,256,65536])
# Count unique colours
n = len(np.unique(I24))
print(n)
< q67
Considering a four dimensions array, how to get sum over the last two axis at once? (★★★)