【力扣hot100题】（054）全排列

挺经典的回溯题的。

class Solution {
public:
    vector<vector<int>> result;
    void recursion(vector<int>& nums,vector<int>& now){
        if(nums.size()==0){
            result.push_back(now);
            return ;
        }
        for(int i=0;i<nums.size();i++){
            now.push_back(nums[i]);
            nums.erase(nums.begin()+i);
            recursion(nums,now);
            nums.insert(nums.begin()+i,now[now.size()-1]);
            now.pop_back();
        }
    }
    vector<vector<int>> permute(vector<int>& nums) {
        vector<int> r;
        recursion(nums,r);
        return result;
    }
};