The correct, optimal and working solution for programming question 3sum on leetcode

class Solution { public: vector<vector<int> > threeSum(vector<int> &num) { int n = num.size(); vector<int> temp; vector< vector<int> > ans; sort(num.begin(), num.end()); for(int i = 0 ; i < (n - 2) ; i++ ) { if( i != 0 && num[i] == num[i-1] ) { continue; } int j = i + 1, k = n - 1; while ( j < k ) { int sum = num[i] + num[j] + num[k]; if( sum == 0 ) { temp.clear(); temp.push_back(num[i]); temp.push_back(num[j]); temp.push_back(num[k]); ans.push_back(temp); j++; k--; while( j < k && num[k] == num[k+1]) { k--; } while(j < k && num[j] == num[j-1] ) { j++; } } else if( sum < 0 ) { j++; } else { k--; } } } /*for( int i = ans.size() - 1 ; i >= 0 ; i-- ) { for( int j = i - 1 ; j >= 0 ; j-- ) { if( ans[i][0] == ans[j][0] && ans[i][1] == ans[j][1] && ans[i][2] == ans[j][2] ) { ans.erase(ans.begin() + j); } } }*/ /*for( set< vector<int> >::iterator itr = s.begin() ; itr != s.end() ; itr++ ) { ans.push_back(*itr); }*/ return ans; } };