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leetcode : 3 sum
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] ]
tag : two pointers
public class Solution { public List<List<Integer>> threeSum(int[] nums) { List<List<Integer>> result = new ArrayList<List<Integer>>(); if(nums == null || nums.length < 3){ return result; } Arrays.sort(nums); for(int i = 0 ; i < nums.length - 2; i++){ int a = nums[i]; if(i != 0 && nums[i-1] == nums[i]){ continue; } int left = i + 1; int right = nums.length - 1; while(left < right){ int b = nums[left]; int c = nums[right]; int sum = a + b + c; if(sum == 0){ List<Integer> tmp = new ArrayList<Integer>(); tmp.add(a); tmp.add(b); tmp.add(c); result.add(tmp); left++; right--; while(left < right && nums[left] == nums[left-1]){ left ++; } while(left < right && nums[right + 1] == nums[right]){ right --; } }else if(a + b + c < 0){ left ++; }else{ right --; } } } return result; } }
leetcode : 3 sum
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