原题链接: http://oj.leetcode.com/problems/4sum/  这道题要求跟3Sum差点儿相同,仅仅是需求扩展到四个的数字的和了.我们还是能够依照3Sum中的解法,仅仅是在外面套一层循环.相当于求n次3Sum.我们知道3Sum的时间复杂度是O(n^2),所以假设这样解的总时间复杂度是O(n^3).代码例如以下: public ArrayList<ArrayList<Integer>> fourSum(int[] num, int target) { Arr…

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.…

最近在准备找工作的算法题,刷刷LeetCode,以下是我的解题报告索引,每一题几乎都有详细的说明,供各位码农参考.根据我自己做的进度持续更新中......                              本文地址 LeetCode:Reverse Words in a String LeetCode:Evaluate Reverse Polish Notation LeetCode:Max Points on a Line LeetCode:Sort List LeetCode:Ins…

Here is my collection of solutions to leetcode problems. Related code can be found in this repo: https://github.com/zhuli19901106/leetcode LeetCode - Course Schedule LeetCode - Reverse Linked List LeetCode - Isomorphic Strings LeetCode - Count Primes…

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.…

转自  http://tech-wonderland.net/blog/summary-of-ksum-problems.html 前言: 做过leetcode的人都知道, 里面有2sum, 3sum(closest), 4sum等问题, 这些也是面试里面经典的问题, 考察是否能够合理利用排序这个性质, 一步一步得到高效的算法. 经过总结, 本人觉得这些问题都可以使用一个通用的K sum求和问题加以概括消化, 这里我们先直接给出K Sum的问题描述和算法(递归解法), 然后将这个一般性的方法套用…

# -*- coding: utf8 -*-'''__author__ = 'dabay.wang@gmail.com' 18: 4Sumhttps://oj.leetcode.com/problems/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 arr…

1. Two Sum 题目链接 题目要求: Given an array of integers, find two numbers such that they add up to a specific target number. The function twoSum should return indices of the two numbers such that they add up to the target, where index1 must be less than ind…

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…