31 lines
553 B
Python
31 lines
553 B
Python
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#!/usr/bin/env python3
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# p -> recursive with lookup table
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# p2 -> count individual combs, add squares, got from forum
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def p(n, tbl=False):
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if n < 3:
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return 1
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if tbl==False:
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tbl = []
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if n-3 >= len(tbl):
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r = 2*p(n-1, tbl) - p(n-2,tbl) + p(n-4, tbl)
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tbl.append(r)
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return tbl[n-3]
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def p2(n):
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if n < 3:
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return 1
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rd = 1
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b1 = b2 = 0
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b3 = 1
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for i in range(3,n):
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b = b3
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b3 += b2
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b2 = b1
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b1 = rd
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rd += b
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return rd+b1+b2+b3
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print(p(50))
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