typedef pair<int,pair<int,int>> scpair;class Solution {public:    int m,n;    vector<vector<int> > threeSum(vector<int> &num) {        n=num.size();        vector<vector<int> > res;        if (n<3) return res;        vector<int> &a=num;        set   <scpair> st;        sort(a.begin(),a.end());        for (int i=0;i<n-2;i++) {            scpair cr;            cr.first=a[i];            int l=i+1;            int r=n-1;            int x=0-a[i];            while(l<r){                int cs=a[l]+a[r];                if (cs<x) l++;                else if(cs>x) r--;                else {                    cr.second.first =a[l];                    cr.second.second=a[r];                    st.insert(cr);                    l++;                }            }        }        for (auto it=st.begin();it!=st.end();it++) {            vector<int> cur(3,0);            cur[0]=it->first;            cur[1]=it->second.first;            cur[2]=it->second.second;            res.push_back(cur);        }        return res;    }};