标签：
Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero.
Note:
For example, given array S = {-1 0 1 2 -1 -4},
A solution set is:
(-1, 0, 1)
(-1, -1, 2)
思路：
和3Sum Closet差不多，只是这次存的是集合。并且如果找到三个数之和等于0的时候，要注意第二个数或者第三个数要变化一下，否则就会陷入死循环中。
题解：
class Solution { public: vector<vector<int> > threeSum(vector<int> &num) { vector<vector<int> > res; vector<int> tmp; sort(num.begin(), num.end()); for(int i=0;i<num.size();i++) { while(i>0 && num[i]==num[i-1]) i++; int l = i+1; int r = num.size()-1; while(l<r) { while(l>i+1 && num[l]==num[l-1]) l++; while(r<num.size()-1 && num[r]==num[r+1]) r--; if(l<r) { int sum = num[i]+num[l]+num[r]; if(sum>0) r--; else if(sum<0) l++; else { tmp.clear(); tmp.push_back(num[i]); tmp.push_back(num[l]); tmp.push_back(num[r]); res.push_back(tmp); l++; } } } } return res; } };
标签：
原文地址：http://www.cnblogs.com/jiasaidongqi/p/4191424.html
