vector<vector<int>> permute(vector<int>& nums) {

vector<vector<int>> result;

dfs(nums, 0, result);

return result;

}

void dfs(vector<int>& nums, int start, vector<vector<int>>& result) {

if (start == nums.size()) {

result.push_back(nums);

return;

}

for (int i = start; i < nums.size(); i++) {

swap(nums[i], nums[start]);

dfs(nums, start + 1, result);

swap(nums[i], nums[start]);

}

}