标签：des style blog color io ar for strong sp
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)
分析：该题的主要思路是：先对num排序，然后最外层循环从第一个元素到倒数第三个元素，循环里用2sum两个指针的解法。此题的难点在于如何remove duplicates。如果在最后对结果除重，会超时，所以要在产生的过程中防止产生重复的triplet。
class Solution { public: vector<vector<int> > threeSum(vector<int> &num) { vector<vector<int>> res; int n = num.size(); if(n < 3) return res; sort(num.begin(), num.end()); for(int i = 0; i < n-2; i++){
//remove duplicates if(i == 0 || (i > 0 && num[i-1] != num[i])){ int left = i+1, right = n-1; while(left < right){ if(num[i] + num[left] + num[right] < 0) left++; else if(num[i] + num[left] + num[right] > 0) right--; else{ res.push_back({num[i], num[left], num[right]}); left++; right--;
//remove duplicates while(left < right && num[left] == num[left-1]) left++; while(left < right && num[right] == num[right+1]) right--; } } } } return res; } };
标签：des style blog color io ar for strong sp
原文地址：http://www.cnblogs.com/Kai-Xing/p/4035330.html
