Permutations II

Code:

class Solution {
public:
    int maxDep;
    vector<int>buf;
    vector<vector<int>> res;
    void dfs(int dep, vector<bool> &valid, vector<int> &num){
        if(dep==maxDep){
            res.push_back(buf);
            return;
        }
        for(int i=0;i<maxDep;i++)
        {
            if(i!=0&&valid[i-1]&&num[i-1]==num[i])
                continue;
            if(valid[i]){
                valid[i]=false;
                buf.push_back(num[i]);
                dfs(dep+1,valid,num);
                valid[i]=true;
                buf.pop_back();
            }
        }
    }
    vector<vector<int>> permuteUnique(vector<int> &num) {
        buf.clear();
        res.clear();
        if(num.empty()) return res;
        sort(num.begin(),num.end()); // sort
        vector<bool> valid(num.size(),true);
        maxDep = num.size();
        dfs(0,valid, num);
        return res;
    }
};