整体思路同之前的一样,依然采取降低维度的方式进行 public List<List<Integer>> solution(int nums[], int target) { List<List<Integer>> result = new ArrayList<>(); if((nums.length<4)||(nums==null)) { return result; } Arrays.sort(nums); if ((4*nums[0]&…

思路一为遍历: public int thirdSolution(int[] nums, int target) { int result = nums[0] + nums[1] + nums[2]; Arrays.sort(nums); for (int i = 0; i < nums.length - 2; i++) { int start = i + 1, end = nums.length - 1; while (start < end) { int tmp = nums[i] + n…

题目 给定一个包含 n 个整数的数组 nums 和一个目标值 target,判断 nums 中是否存在四个元素 a,b,c 和 d ,使得 a + b + c + d 的值与 target 相等?找出所有满足条件且不重复的四元组. 注意: 答案中不可以包含重复的四元组. 解题思路 将nums数组重新排列,然后从i = 0开始遍历,分别取j = i + 1.left = j + 1和right = nums.length - 1,将nums[i].nums[j].nums[left]和nums[r…

2017/11/3 Leetcode 日记 654. Maximum Binary Tree Given an integer array with no duplicates. A maximum tree building on this array is defined as follow: The root is the maximum number in the array.(根节点是数组中的最大值) The left subtree is the maximum tree const…

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…

2017/11/22 Leetcode 日记 136. Single Number Given an array of integers, every element appears twice except for one. Find that single one. class Solution { public: int singleNumber(vector<int>& nums) { int len = nums.size(); ]; ; i < len; i++){…

2017/11/21 Leetcode 日记 496. Next Greater Element I You are given two arrays (without duplicates) nums1 and nums2 where nums1’s elements are subset of nums2. Find all the next greater numbers for nums1's elements in the corresponding places of nums2.…

2017/11/13 Leetcode 日记 463. Island Perimeter You are given a map in form of a two-dimensional integer grid where 1 represents land and 0 represents water. Grid cells are connected horizontally/vertically (not diagonally). The grid is completely surro…

2017/11/14 Leetcode 日记 442. Find All Duplicates in an Array Given an array of integers, 1 ≤ a[i] ≤ n (n = size of array), some elements appear twice and others appear once. Find all the elements that appear twice in this array. Could you do it withou…

2017/11/9 Leetcode 日记 566. Reshape the Matrix In MATLAB, there is a very useful function called 'reshape', which can reshape a matrix into a new one with different size but keep its original data. You're given a matrix represented by a two-dimensiona…

2017/11/7 Leetcode 日记 669. Trim a Binary Search Tree Given a binary search tree and the lowest and highest boundaries as L and R, trim the tree so that all its elements lies in [L, R] (R >= L). You might need to change the root of the tree, so the re…

2017/11/6 Leetcode 日记 344. Reverse String Write a function that takes a string as input and returns the string reversed. class Solution { public: string reverseString(string s) { , sz = s.size()-; ; i < sz; i++, sz--){ char temp = s[i]; s[i] = s[sz];…

2017/11/5 Leetcode 日记 476. Number Complement Given a positive integer, output its complement number. The complement strategy is to flip the bits of its binary representation. Note: The given integer is guaranteed to fit within the range of a 32-bit s…

根据题目可知,输入为:一个相邻元素不相等的数列,输出为:其中一个(上)峰值的序号.并且要求时间复杂度为logn 分析:由于题目要求时间复杂度为logn,因此不能进行全部遍历.又因为只需要找到其中的一个峰值,那么,每次对半分,便可以达到logn的复杂度. 根据对半分的思路继续想,不难发现只要确定了中间位置的数是处在上升阶段还是下降阶段,就可以确定在某一侧必有一个峰值. 往复多次,即可找出两个点,其中一个一定处于某一个峰值上. java代码: public int findPeakElement(i…

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. 解题思路一: 四路夹逼,C++: class Solution { public: vector<vector<int> > fou…

问题描述: 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…

题目链接 https://leetcode.com/problems/4sum/?tab=Description 找到数组中满足 a+b+c+d=0的所有组合,要求不重复. Basic idea is using subfunctions for 3sum and 2sum, and keeping throwing all impossible cases. O(n^3) time complexity, O(1) extra space complexity. 首先进行判断,由于是四个数相加…

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.…

题目: Given an array of integers and an integer k, find out whether there are two distinct indices i and j in the array such that nums[i] = nums[j] and the difference between i and jis at most k. 给定一个整形数组和一个整数型数k,找出在这个数组中是否存在两个相同的数,并且这两个数的下标的距离小于k. "&q…

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 exampl…

一.题目链接:https://leetcode.com/problems/4sum/ 二.题目大意: 给定一个数组A和一个目标值target,要求从数组A中找出4个数来使之构成一个4元祖,使得这四个数的和等于target,找出所有的四元组,当然这些四元组不能有重复的. 三.题解: 这道题实质就是3sum的变形,关于4sum问题,已经在https://www.cnblogs.com/wangkundentisy/p/9079622.html这里说过了,无外乎最外面两层循环,最里面的循环使用哈希表或…

454. 4Sum II Add to List Description Submission Solutions Total Accepted: 8398 Total Submissions: 18801 Difficulty: Medium Contributors: Samuri Given four lists A, B, C, D of integer values, compute how many tuples (i, j, k, l) there are such that A[…

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 exampl…

leetcode 237. 删除链表中的节点 链接:https://leetcode-cn.com/problems/delete-node-in-a-linked-list/ 示例 : 输入: head = [4,5,1,9], node = 5输出: [4,1,9]解释: 给定你链表中值为 5 的第二个节点,那么在调用了你的函数之后,该链表应变为 4 -> 1 -> 9. 这道题比较简单,修改之前节点的 next 指针,使其指向之后的节点: /** * Definition for sin…

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 of n integers where n > 1, nums, return an array output such that output[i] is equal to the product of all the elements of nums except nums[i]. Solve it without division and in O(n). For example, given [1,2,3,4], return [24,12,8,6]. 题目…

题目: Given an integer array with all positive numbers and no duplicates, find the number of possible combinations that add up to a positive integer target. Example: nums = [1, 2, 3] target = 4 The possible combination ways are: (1, 1, 1, 1) (1, 1, 2)…

题目 Given an array of integers, find if the array contains any duplicates. Your function should return true if any value appears at least twice in the array, and it should return false if every element is distinct. Subscribe to see which companies ask…

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…

java中的集合框架图 如图所示:java中的集合分为两种Collection和Map两种接口 可分为Collection是单列集合和Map的双列集合 Collection单列集合:继承了Iterator接口所以具有了iterator()方法 ,该方法返回一个Iterator<T>,这个接口具有 HasNext (),next(),remove()3个方法可以在实现类里完成实现. hasNext():判断是否有下一个元素 cusor是当前的操作下标 next():读取下一个元素 remove(…