Created
April 8, 2018 00:27
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""" Given the first 10 numbers, we want to know how many snake permutations exist, where a snake permutations is: | |
x1 < x2 > x3 < x4 > x5 < x6 > x7 < x8 > x9 < x10 | |
The result is very counterintuitive....more than 50000 snake permutation exist. | |
It takes a lot of time to have the output, so take only the idea of the code...""" | |
import random | |
union = [] | |
for i in range (25000000): | |
A = [s for s in range (1,11)] | |
new = [] | |
for i in range(10): | |
k = random.choice(A) | |
new.append(k) | |
A.remove(k) | |
count = 0 | |
for i in range(0,8,2): | |
if new[i] < new[i+1] and new[i+1] > new[i+2] and new[8] < new[9]: # the algorithm to search the snake permutaton | |
count += 1 | |
if count == 4 and new not in union: | |
union.append(new) | |
print(union) | |
print() | |
print("For n = 10 there are: {} snakes permutations".format(len(union))) |
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