51 lines
1.0 KiB
Python
51 lines
1.0 KiB
Python
#!/usr/bin/env python3
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# 145 is a curious number, as 1! + 4! + 5! = 1 + 24 + 120 = 145.
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#
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# Find the sum of all numbers which are equal to the sum of the factorial of their digits.
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#
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# Note: as 1! = 1 and 2! = 2 are not sums they are not included.
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from math import factorial
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from timeit import default_timer
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from numpy import ones
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def main():
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start = default_timer()
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a = 10
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sum_ = 0
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factorials = ones(10, int)
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# Pre-calculate factorials of each digit from 0 to 9.
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for i in range(2, 10):
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factorials[i] = factorial(i)
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# 9!*7<9999999, so 9999999 is certainly un upper bound.
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while a < 9999999:
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b = a
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sum_f = 0
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while b != 0:
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digit = b % 10
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b = b // 10
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sum_f = sum_f + factorials[digit]
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if a == sum_f:
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sum_ = sum_ + a
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a = a + 1
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end = default_timer()
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print('Project Euler, Problem 34')
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print(f'Answer: {sum_}')
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print(f'Elapsed time: {end - start:.9f} seconds')
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if __name__ == '__main__':
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main()
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