46 Permutations

Given a collection of distinct 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],
  [3,2,1]
]

Solution (recursive):

class Solution {
public:
    vector<vector<int>> permute(vector<int>& nums) {
        int n = nums.size();
        vector<vector<int>> res;
        if ( n == 0 ) {
            vector<int> tmp;
            res.push_back(tmp);
            return res;
        }
        for ( int i = 0; i <= n-1; i++) {
            vector<int> tmp;
            for ( int j = 0; j <= n-1; j++ ) {
                if ( i != j ) tmp.push_back(nums[j]);
            }
            vector<vector<int>> tmp_res = permute(tmp);
            int nres = tmp_res.size();
            for ( int j = 0; j <= nres-1; j++ ) {
                tmp = tmp_res[j];
                tmp.push_back(nums[i]);
                res.push_back(tmp);
            }
        }
        return res;
    }
};

Solution (iterative):???