15. 3Sum
- Total Accepted: 130571
- Total Submissions: 670539
- Difficulty: Medium
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: The solution set must not contain duplicate triplets.
For example, given array S = [-1, 0, 1, 2, -1, -4], A solution set is: [ [-1, 0, 1], [-1, -1, 2] ]
思路:基本思路和Leetcode 16. 3Sum Closest类似,但要注意去除集合元素完全相同的集合,就是去除相同集合。
代码:
class Solution { public: vector<vector<int>> threeSum(vector<int>& nums) { sort(nums.begin(),nums.end()); vector<vector<int>> res; int i,j,k,n=nums.size(),temp; for(i=0;i<n;i++){ j=i+1; k=n-1; while(j<k){ int ans=nums[i]+nums[j]+nums[k]; if(ans==0){ res.push_back({nums[i],nums[j],nums[k]}); while(j<k&&nums[j]==nums[j+1]) j++; while(k>j&&nums[k]==nums[k-1]) k--; } if(ans>=0) k--; if(ans<=0) j++; } while(i+1<n&&nums[i]==nums[i+1]) i++; } return res; } };