[英]How to perform polynomial addition and multiplication using python 3.x?
例如3x^4 - 17x^2 - 3x + 5
。 多項式的每個項可以表示為一對整數(系數,指數)。 即[(3,4),(-17,2), (-3,1), (5,0)]
我們具有以下約束條件,以確保每個多項式都有唯一的表示形式:
為以下操作編寫Python函數:
addpoly(p1,p2)
multpoly(p1,p2)
一些例子:
>>> addpoly( [(4,3),(3,0)], [(-4,3),(2,1)] )
[(2, 1),(3, 0)]
說明: (4x^3 + 3) + (-4x^3 + 2x) = 2x + 3
>>> addpoly( [(2,1)], [(-2,1)] )
[]
說明: 2x + (-2x) = 0
>>> multpoly( [(1,1),(-1,0)], [(1,2),(1,1),(1,0)] )
[(1, 3),(-1, 0)]
說明: (x - 1) * (x^2 + x + 1) = x^3 - 1
您想定義一個函數,該函數接受任意數量的形式的參數
[(4,3),(3,0)], [(-4,3),(2,1)]
addpoly
可以通過collections.defaultdict
輕松完成:
from collections import defaultdict
def addpoly(*polynoms):
result = defaultdict(int)
for polynom in polynoms:
for factor, exponent in polynom:
result[exponent] += factor
return [(coeff, exponent) for exponent, coeff in result.items() if coeff]
In [68]: addpoly([(4,3),(3,0)],[(-4,3),(2,1)])
Out[68]: [(3, 0), (2, 1)]
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