leetcode/code/lc15.java at master · mJackie/leetcode · GitHub

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package code;

* 15. 3Sum

* 题意：找出数组中所有和为0的三元组合

* 难度：Medium

* 分类：Array, Two Pointers

* 注意：如何避免 List 重复元素

* Tips：lc15, lc16, lc923

import java.util.*;

public class lc15 {

public static void main(String[] args) {

int[] nums = {-1, 0, 1, 2, -1, -4};

System.out.println(threeSum(nums).toString());

}

public static List<List<Integer>> threeSum(int[] nums) {

List<List<Integer>> result = new ArrayList();

Arrays.sort(nums);

for (int i = 0; i < nums.length-2 ; i++) {

if( i>0 && nums[i]==nums[i-1] ) //防止重复添加相同内容List

continue;

int left = i+1, right = nums.length-1;

while(left<right){

if( nums[i]+nums[left]+nums[right] == 0 ){

result.add(Arrays.asList(nums[i],nums[left],nums[right])); //Arrays.asList(int a, int b, intc);

while(left<right && nums[left]==nums[left+1]) //防止重复添加相同内容List

left++;

while(left<right && nums[right]==nums[right-1]) //防止重复添加相同内容List

right--;

left++;

right--;

}else if( nums[i]+nums[left]+nums[right] < 0 )

left++;

else

right--;

}

return result;

}

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