Leetcode 39： python可变类型复制（浅拷贝和深拷贝）

刚刚在leetcode上写了一道算法题：39. Combination Sum，因为踩了python中复制的坑，花了很长时间才爬出来=。=

题目：

Given a set of candidate numbers (C) (without duplicates) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.

The same repeated number may be chosen from C unlimited number of times.

起因是用python做完题后看了一下c++的解法:

class Solution {
public:
    std::vector<std::vector<int> > combinationSum(std::vector<int> &candidates,