047.md

47. Permutations II

Solution 1

// DFS
class Solution {
public:
    vector<vector<int>> permuteUnique(vector<int>& nums) {
        sort(nums.begin(), nums.end());
        bool used[nums.size()];
        for (int i = 0; i < nums.size(); i++)
            used[i] = false;
        vector<int> cur;
        vector<vector<int>> ans;
        _permute(nums, used, cur, ans);
        return ans;
    }

    void _permute(vector<int>& nums, bool* used,
                  vector<int>& cur, vector<vector<int>>& ans) {
        if (cur.size() == nums.size()) {
            ans.push_back(cur);
            return;
        }
        for (int i = 0; i < nums.size(); i++) {
            if (used[i])
                continue;
            if (i > 0 && nums[i] == nums[i - 1] && !used[i - 1])
                continue;
            used[i] = true;
            cur.push_back(nums[i]);
            _permute(nums, used, cur, ans);
            cur.pop_back();
            used[i] = false;
        }
    }
};