python - 我怎样才能更有效地编写这个解决方案？

Question

import random

a = [int(1000*random.random()) for i in xrange(10)]
b = [int(1000*random.random()) for i in xrange(10)]
c = [int(1000*random.random()) for i in xrange(10)]
d = dict()
for i in xrange(len(a)):
    for j in xrange(len(b)):
        for k in xrange(len(c)):
            if (i+j+k == 10):
                d[(i,j,k)] = a[i]+b[j]+c[k]

print max(d.values())

该代码找到 a,b,c 中元素的最佳三元组，使得 a[i]+b[j]+b[k] 和 i+j+k=10 成立

Answer 1

首先，您可以更改循环的边界并摆脱最内层的循环:

import random
a = [int(1000*random.random()) for i in xrange(10)]
b = [int(1000*random.random()) for i in xrange(10)]
c = [int(1000*random.random()) for i in xrange(10)]
d = dict()
for i in xrange(10):
    for j in xrange(10 - i):
        k = 10 - i - j
        if k < len(c):
            d[(i,j,k)] = a[i]+b[j]+c[k]

print max(d.values())

这将运行时间提高了约 4.5 倍:

In [2]: %timeit original()
10000 loops, best of 3: 166 us per loop

In [3]: %timeit new()
10000 loops, best of 3: 36.1 us per loop