3Sum

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]]

Subscribe to see which companies asked this question

package leetcode;import java.util.ArrayList;import java.util.Arrays;import java.util.List;/** *  * @author Mouse * */public class Solution {public static List<List<Integer>> threeSum(int[] nums) {List<List<Integer>> result = new ArrayList<>();if (nums == null || nums.length < 3)return result;Arrays.sort(nums);// 给nums排序for (int i = 0; i < nums.length - 2; i++) {if (i > 0 && nums[i] == nums[i - 1])continue;int left = i + 1;int right = nums.length - 1;while (left < right) {int sum = nums[left] + nums[right] + nums[i];if (sum == 0) {List<Integer> arr = new ArrayList<Integer>();arr.add(nums[left]);arr.add(nums[right]);arr.add(nums[i]);result.add(arr);//去重复的while (left < right && nums[left + 1] == nums[left])left++;//继续找left++;while (left < right && nums[right - 1] == nums[right])right--;right--;} else if (sum > 0) {right--;} else {left++;}}}return result;}public static void main(String[] args) {int[] nums = { -4, -2, -2, -2, 0, 1, 2, 2, 2, 3, 3, 4, 4, 6, 6 };List<List<Integer>> a = threeSum(nums);System.out.println(a);}}