题目描述 给出一个有n个元素的数组S,S中是否有元素a,b,c和d满足a+b+c+d=目标值?找出数组S中所有满足条件的四元组. 注意: 四元组(a.b.c.d)中的元素必须按非降序排列.(即a≤b≤c≤d) 解集中不能包含重复的四元组. 例如:给出的数组 S = {1 0 -1 0 -2 2}, 目标值 = 0.↵↵ 给出的解集应该是:↵ (-1, 0, 0, 1)↵ (-2, -1, 1, 2)↵ (-2, 0, 0, 2) Given an array S of n integers, a…

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.…

3Sum Closest Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. You may assume that each input would have exactly one solution. For example, given arr…

18. 4Sum 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 For example, given array S = [1, 0, -1, 0, -2, 2], and targ…

问题: 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. For ex…

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: Elements in a triplet (a,b,c) must be in non-descending order. (ie, a ≤ b ≤ c) The…

3 Sum Given an array S of n integers, are there elements a, b, c in Ssuch that a + b + c = 0? Find all unique triplets in the array which gives the sum of zero. Notice Elements in a triplet (a,b,c) must be in non-descending order. (ie, a ≤ b ≤ c) The…

4Sum 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 o…

2sum 如果数组是无序的,先排序(n*logn),然后用两个指针i,j,各自指向数组的首尾两端,令i=0,j=n-1,然后i++,j--,逐次判断a[i]+a[j]?=sum,如果某一刻a[i]+a[j]>sum,则要想办法让sum 的值减小,所以此刻i 不动,j--,如果某一刻a[i]+a[j]<sum,则要想办法让sum 的值增大,所以此刻i++,j 不动.所以,数组无序的时候,时间复杂度最终为O(n*logn+n)=O(n*logn),若原数组是有序的,则不需要事先的排序,直接O(n)…