LeetCode--4Sum & 总结 前言 有人对 Leetcode 上 2Sum,3Sum,4Sum,K Sum问题作了总结: http://blog.csdn.net/nanjunxiao/article/details/12524405 对于同类问题做了代码模型: int i = starting; //头指针 int j = num.size() - 1; //尾指针 while(i < j) { int sum = num[i] + num[j]; if(sum == targe…

Given four lists A, B, C, D of integer values, compute how many tuples (i, j, k, l) there are such that A[i] + B[j] + C[k] + D[l] is zero. To make problem a bit easier, all A, B, C, D have same length of N where 0 ≤ N ≤ 500. All integers are in the r…

Given an array S of n integers, are there elements a, b, c, and d in S such that a + b + c + d = target? Find all unique quadruplets in the array which gives the sum of target. Note: Elements in a quadruplet (a,b,c,d) must be in non-descending order.…

import java.util.Arrays; import java.util.HashSet; import java.util.Set; /** * Source : https://oj.leetcode.com/problems/4sum/ * * Created by lverpeng on 2017/7/10. * * Given an array S of n integers, are there elements a, b, c, and d in S such that…

题意:这是继2sum和3sum之后的4sum,同理,也是找到所有4个元素序列,满足他们之和为target.以vector<vector<int>>来返回,也就是二维的,列长为4,有多少个序列就多少行,每行都是唯一的,且升序. 思路: 方法一:用类似3sum的方法,先确定下第1个元素,再确定第2个元素,剩下两个元素用“两个指针”.前提是已排序.这个方法主要是怎么去重,这里提供两种方法: 1)用unordered_set,只要找到一个序列就检查里面有没有这样的序列,若没有就插入,这样保…

Given an array S of n integers, are there elements a, b, c, and d in S such that a + b + c + d = target? Find all unique quadruplets in the array which gives the sum of target. Note: Elements in a quadruplet (a,b,c,d) must be in non-descending order.…

Given four lists A, B, C, D of integer values, compute how many tuples (i, j, k, l) there are such that A[i] + B[j] + C[k] + D[l] is zero. To make problem a bit easier, all A, B, C, D have same length of N where 0 ≤ N ≤ 500. All integers are in the r…

class Solution(object): def fourSum(self, nums, target): """ :type nums: List[int] :type target: int :rtype: List[List[int]] """ numLen=len(nums) if numLen <= 3: return list() nums.sort() res,d=set(),{} for p in xrange(num…

题意 Given an array S of n integers, are there elements a, b, c, and d in S such that a + b + c + d = target? Find all unique quadruplets in the array which gives the sum of target. 给定一个数组,找出其中的四个数,使它们的和等于某个特定的数 解法 和2Sum以及3Sum一样,都是先排序然后遍历前面几个数,剩下的两个数用T…

1. Question Given an array S of n integers, are there elements a, b, c, and d in S 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…