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