該題就是三數(shù)之和為模板的題

    vector<vector<int> > findTriplets(vector<int>& num) {
        // write code here
        vector<vector<int>> res;
        if(num.size()<3) return res;
        sort(num.begin(),num.end());
        for(int i=0;i<num.size()-2;i++){
            if(num[i]==num[i-1] && i) continue;
            int l=i+1,r=num.size()-1;
            while (l<r) {
                if (num[l]+num[r]==-num[i]) {
                    res.push_back({num[i],num[l],num[r]});
                    while (num[l]==num[l+1] && l+1<r) {
                        l++;
                    }
                    while (num[r]==num[r-1] && r-1>l) {
                        r--;
                    }
                    l++,r--;
                }else if (num[l]+num[r]>-num[i]) {
                    r--;
                }else l++;
            }

        }
        return res;
    }
};