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class Solution {
public:
    vector<vector<int>> permute(vector<int>& nums) {
        vector<vector<int>> ans;
        permute(nums, 0, ans);
        return ans;
    }

    void permute(vector<int> &nums, int idx, vector<vector<int>> &ans){
        if(idx == nums.size()){
            ans.push_back(nums);
        }
        for(int i=idx; i<nums.size(); i++){
            swap(nums[i], nums[idx]);
            permute(nums, idx+1, ans);
            swap(nums[i], nums[idx]);
        }
    }
};