[各种面试题] threesum

typedef tuple<int, int, int> ABC; //存放a,b,c三元组//返回所有满足条件的(a,b,c)三元组vector<ABC> threeSumZero(vector<int> &arr) {vector<ABC> ret;if ( arr.size()<3 )return ret;sort(arr.begin(),arr.end());for(int t=arr.size()-1;t>=2;){int target=0-arr[t];int l=0,r=t-1;while(l<r){int sum=arr[l]+arr[r];if ( sum == target ){ret.push_back(ABC(arr[l],arr[r],arr[t]));int tmp=arr[l];while(arr[l]==tmp&&l<r )l++;}else if ( sum<target)l++;elser--;}int tmp=arr[t];while(t>=2&&arr[t]==tmp)t--;}return ret;}