【题目】
Given an array nums
of n integers and an integer target
, are there elements a, b, c, and d in nums
such that a + b + c + d = target
? Find all unique quadruplets in the array which gives the sum of target
.
Note:The solution set must not contain duplicate quadruplets.
【思路】
和leetcode15三数之和3 Sum类似https://www.cnblogs.com/inku/p/9955638.html
多一次循环,加粗部分是新增的
重点是去重。
【代码】
class Solution { public List<List<Integer>> fourSum(int[] nums, int target) { List<List<Integer>> data=new ArrayList<>(); Arrays.sort(nums); for(int i=0;i<nums.length-2;i++){ for(int j=nums.length-1;j>0;j--){ int left=i+1; int right=j-1; if(i>0&&nums[i]==nums[i-1]){ continue;} if(j<nums.length-1&&nums[j]==nums[j+1]){ continue;} while(left<right){ int sum=nums[left]+nums[right]+nums[i]+nums[j]; if(sum==target){ data.add(Arrays.asList(nums[left], nums[right],nums[i],nums[j])); left++; right--; while(left<right&&nums[left]==nums[left-1]) left++; while(left<right&&nums[right]==nums[right+1]) right--; } else if(left<right&&sum>target) right--; else left++; } } } return data; } }
原文地址:https://www.cnblogs.com/inku/p/9977917.html
时间: 2024-10-07 14:20:18