Leetcode#15 3Sum

Original title Address

With 2sum, 3sum, 4sum, 3sum closest series, see this article

Sort +dfs+ Pruning + two-point search

What if the last element does not have a binary lookup time out??

Code:

1vector<vector<int> >Res;2 3 voidDFS (vector<int> &num, vector<int> ans,intPosintLeftintsum) {4   if(left = =0) {5     if(Sum = =0)6 res.push_back (ans);7     return;8   }9 Ten   if(left = =1) { One     intL =Pos; A     intR = num.size ()-1; -      while(L <=r) { -       intm = (L + r)/2; the       if(Num[m] + sum = =0) { - Ans.push_back (num[m]); - res.push_back (ans); - Ans.pop_back (); +         return; -       } +       Else if(Num[m] + sum <0) AL = m +1; at       Else -r = M-1; -     } -     return; -   } -  inunordered_set<int>Old ; -    for(inti = pos; I < num.size (); i++) { to     if(Old.find (num[i])! =old.end ()) +       Continue; -     if(Sum + Left * Num[i] >0) the        Break; *     if(sum + num[i] + (left-1) * Num[num.size ()-1] <0) $       Continue;Panax Notoginseng Old.insert (Num[i]); - Ans.push_back (Num[i]); theDFS (num, ans, i +1, left-1, Sum +num[i]); + Ans.pop_back (); A   } the } +  -vector<vector<int> > Threesum (vector<int> &num) { $ sort (Num.begin (), Num.end ()); $DFS (NUM, vector<int> (),0,3,0); -   returnRes; -}

Leetcode#15 3Sum