48 lines
873 B
Python
48 lines
873 B
Python
#!/usr/bin/env python3
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# The Fibonacci sequence is defined by the recurrence relation:
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#
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# Fn = Fn−1 + Fn−2, where F1 = 1 and F2 = 1.
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# Hence the first 12 terms will be:
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# F1 = 1
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# F2 = 1
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# F3 = 2
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# F4 = 3
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# F5 = 5
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# F6 = 8
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# F7 = 13
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# F8 = 21
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# F9 = 34
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# F10 = 55
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# F11 = 89
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# F12 = 144
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#
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# The 12th term, F12, is the first term to contain three digits.
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#
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# What is the index of the first term in the Fibonacci sequence to contain 1000 digits?
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from projecteuler import timing
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@timing
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def p025() -> None:
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fib1 = 1
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fib2 = 1
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fibn = fib1 + fib2
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i = 3
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# Calculate the Fibonacci numbers until one with 1000 digits is found.
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while len(str(fibn)) < 1000:
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fib1 = fib2
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fib2 = fibn
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fibn = fib1 + fib2
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i = i + 1
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print('Project Euler, Problem 25')
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print(f'Answer: {i}')
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if __name__ == '__main__':
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p025()
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