[LeetCode] 15. 3Sum
2016-10-01 21:59 amadis 阅读(116) 评论(0) 编辑 收藏 举报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] ]
1 class Solution { 2 public: 3 vector<vector<int>> threeSum(vector<int>& nums) { 4 vector<vector<int>> ret; 5 6 sort(nums.begin(), nums.end()); 7 8 for (int i = 0; i < nums.size(); i++){ 9 // if i is scanced already, skip it 10 if (i > 0 && nums[i] == nums[i-1]) continue; 11 int left = i + 1; 12 int right = nums.size() - 1; 13 while (left < right){ 14 if ((nums[left] + nums[right]) < -nums[i]){ 15 left++; 16 }else if ((nums[left] + nums[right]) > -nums[i]){ 17 right--; 18 }else{ 19 vector<int> tmp; 20 tmp.push_back(nums[i]); 21 tmp.push_back(nums[left]); 22 tmp.push_back(nums[right]); 23 ret.push_back(tmp); 24 left++; 25 right--; 26 // remove duplicates! 27 while(nums[left] == nums[left - 1]) left++; 28 while(nums[right] == nums[right+1]) right--; 29 } 30 } 31 } 32 33 return ret; 34 } 35 };