Permutations

Given a collection of numbers, return all possible permutations.

For example,
[1,2,3] have the following permutations:
[1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], and [3,2,1].

思路：这题和string permutation差不多，依旧是枚举互换的位置。

class Solution {
public:
    void permuteRecur(vector<vector<int> >& res, int st_loc, vector<int>& aim)
    {
        if (st_loc >= aim.size())
            res.push_back(aim);
        else
        {
            for (int i = st_loc, n = aim.size(); i < n; i++)
            {
                swap(aim[st_loc], aim[i]);
                permuteRecur(res, st_loc + 1, aim);
                swap(aim[st_loc], aim[i]);
            }
        }
    }
    vector<vector<int>> permute(vector<int>& nums) {
        vector<vector<int> > res;
        permuteRecur(res, 0, nums);
        return res;
    }
};