回溯算法：全排列问题

回溯算法：全排列问题

思路：利用一个数组进行去重

class Solution {
public:
    vector<vector<int>> res;
    vector<int> path;
    vector<int> use;
    vector<vector<int>> permute(vector<int>& nums) {
        int step = 0;
        use.assign(nums.size(), 0);
        backtrack(nums, step);
        return res;
    }
    void backtrack(vector<int>& nums, int step)
    {
        if(step == nums.size())
        {
            res.push_back(path);
            return;
        }
        for(int i = 0; i < nums.size(); i++)
        {
            //相同则跳过
            if(use[i] == 1)
            {
                continue;
            }
            //递归下一层
            use[i] = 1;
            step++;
            path.push_back(nums[i]);
            backtrack(nums,step);
            //回溯
            step--;
            use[i] = 0;
            path.pop_back();
        }
    }
};