24 lines
480 B
Python
24 lines
480 B
Python
#!/usr/bin/env python3
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def fib(n):
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if n >= 0:
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return fibiter(1, 0, 0, 1, n)
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if n < 0:
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a, b = 0, 1
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for _ in range(0, n, -1):
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a, b = b - a, a
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return a
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def fibiter(a, b, p, q, count):
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if count == 0:
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return b
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if count % 2 == 0:
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return fibiter(a, b, p * p + q * q, q * q + 2 * p * q, count / 2)
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else:
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return fibiter(b * q + a * q + a * p, b * p + a * q, p, q, count - 1)
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print(fib(1000000))
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