题解 | #有重复项数字的全排列#

class Solution {
public:

    vector<vector<int> > result;
    vector<vector<int> > permuteUnique(vector<int> &num) {
        if (num.size() == 0) return result;
        sort(num.begin(), num.end());
        vector<bool> state(num.size(), false);
        vector<int> tmp;
        back_tracking(num, tmp, state);
        return result;
    }
    void back_tracking(vector<int>& num, vector<int>& tmp, vector<bool>& state) {
        if (tmp.size() == num.size()) {
            result.push_back(tmp);
            return;
        }
        for (int i = 0; i < num.size(); ++i) {
            if (state[i] || (i > 0 && num[i] == num[i-1] && state[i-1])) {
                continue;
            }
            state[i] = true;
            tmp.push_back(num[i]);
            back_tracking(num, tmp, state);
            state[i] = false;
            tmp.pop_back();
        }
        return;
    }
    
};