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Knights Code
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import functools | |
moves = { | |
0: [4, 6], | |
1: [6, 8], | |
2: [7, 9], | |
3: [4, 8], | |
4: [0, 3, 9], | |
5: [], | |
6: [0, 1, 7], | |
7: [2, 6], | |
8: [1, 3], | |
9: [2, 4], | |
} | |
def memoize(func): | |
"""NB, this memoize implementation isn't thread-safe and won't memoize | |
functions with named parameters. | |
""" | |
memo = {} | |
@functools.wraps(func) | |
def wrapper(*args): | |
if args not in memo: | |
memo[args] = func(*args) | |
return memo[args] | |
return wrapper | |
@memoize | |
def count_codes(remaining_length, ending_digit): | |
if remaining_length == 1: | |
return 1 | |
return sum(count_codes(remaining_length - 1, d) for d in moves[ending_digit]) | |
if __name__ == '__main__': | |
target_length = 12 | |
print sum(count_codes(target_length, end) for end in moves) |
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