39 lines
975 B
Python
39 lines
975 B
Python
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#!/usr/bin/env python
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# -*- coding: utf-8 -*-
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"""
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Obliczenie n-tego wyrazu ciągu fibonacciego na dwa sposoby.
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1. Naiwna rekurencja: podstawienie do wzoru.
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2. Wersja z cachem: każdy wyraz jest obliczany dokładnie raz.
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"""
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def naive_fibonacci(n):
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if n <= 0:
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return 0
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if n in [1,2]:
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return 1
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return naive_fibonacci(n-1) + naive_fibonacci(n-2)
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def cache_fibonacci(n, cache=None):
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if cache is None:
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cache = [None for i in range(n+1)]
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cache[0] = 0
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cache[1] = cache[2] = 1
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return cache_fibonacci(n, cache)
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else:
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if cache[n] is not None:
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return cache[n]
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else:
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cache[n] = cache_fibonacci(n-1, cache) + cache_fibonacci(n-2, cache)
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return cache[n]
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def non_reccurent_fibonacci(n):
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cache = [None for i in range(n+1)]
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cache[0] = 0
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cache[1] = cache[2] = 1
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for i in range(2, n + 1):
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cache[i] = cache[i-1] + cache[i-2]
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return cache[n]
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