LeetCode解题报告:Linked List Cycle && Linked List Cycle II 1题目 Linked List Cycle Given a linked list, determine if it has a cycle in it. Follow up: Can you solve it without using extra space? Linked List Cycle II Given a linked list, return the node w…

描述 Follow up for "Remove Duplicates": What if duplicates are allowed at most twice? For example, Given sorted array A = [1,1,1,2,2,3], Your function should return length = 5, and A is now [1,1,2,2,3] 解法一 要解该题,只需要在上一题(leetcode解题报告(1):Remove Dupli…

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…

描述 Given an index k, return the kth row of the Pascal's triangle. For example, given k = 3, Return [1,3,3,1]. 分析 先构造了一个杨辉三角,然后返回这个杨辉三角的最后一组值,没超时就万事大吉了... 感觉可以用递归写,但是嫌麻烦,放弃了. 代码如下: class Solution { public: vector<int> getRow(int rowIndex) { vector<…

描述 Given numRows, generate the first numRows of Pascal's triangle. For example, given numRows = 5, Return [ [1], [1,1], [1,2,1], [1,3,3,1], [1,4,6,4,1]] 分析 其实就是杨辉三角,以前用队列写过. 为了和numRows相匹配,以变量i代表当前的行数,那么i-1才是当前行的下标.以j代表当前行的第i个元素(这个j是从下标1开始的). 代码如下: cl…

题目一: Longest Substring Without Repeating Characters Given a string, find the length of the longest substring without repeating characters. For example, the longest substring without repeating letters for "abcabcbb" is "abc", which the…

Given a string containing just the characters '(' and ')', find the length of the longest valid (well-formed) parentheses substring. Example 1: Input: "(()" Output: 2 Explanation: The longest valid parentheses substring is "()" Example…

1. Search in Rotated Sorted Array Suppose an array sorted in ascending order is rotated(轮流,循环) at some pivot(枢轴; 中心点) unknown to you beforehand(提前; 事先). (i.e., 0 1 2 4 5 6 7 might become 4 5 6 7 0 1 2). You are given a target value to search. If foun…

1. Longest Palindromic Substring Given a string s, find the longest palindromic substring in s. You may assume that the maximum length of s is 1000. Example: Input: "babad" Output: "bab" Note: "aba" is also a valid answer. Ex…

1. 1-bit and 2-bit Characters We have two special characters. The first character can be represented by one bit 0. The second character can be represented by two bits (10 or 11). Now given a string represented by several bits. Return whether the last…

前言: 这几天在做LeetCode 里面有2sum, 3sum(closest), 4sum等问题, 这类问题是典型的递归思路解题.该这类问题的关键在于,在进行求和求解前,要先排序Arrays.sort()可实现,而本文则着重探讨关于KSum问题. leetcode求和问题描写叙述(K sum problem): K sum的求和问题通常是这样子描写叙述的:给你一组N个数字(比方 vector num), 然后给你一个常数(比方 int target) ,我们的goal是在这一堆数里面找到K个数…

描述 Given an array of integers and an integer k, you need to find the number of unique k-diff pairs in the array. Here a k-diff pair is defined as an integer pair (i, j), where i and j are both numbers in the array and their absolute difference is k.…

作者: 负雪明烛 id: fuxuemingzhu 个人博客: http://fuxuemingzhu.cn/ 把自己刷过的所有题目做一个整理,并且用简洁的语言概括了一下思路,汇总成了一个表格. 题目的排列顺序是按照先Easy再Medium再Hard排列的,暂时还没有把题目全部整理完成.后序我会把刷过的所有的题目都整理到这个文档里. 题目 难度 解法 题目地址 566. Reshape the Matrix Easy 变长数组,求余法,维护行列计算在新的数组中的位置 https://blog.c…

Given a string s and a dictionary of words dict, determine if s can be segmented into a space-separated sequence of one or more dictionary words. For example, givens = "leetcode",dict = ["leet", "code"]. Return true because &…

1 题目描述 Write an algorithm to determine if a number is "happy". A happy number is a number defined by the following process: Starting with any positive integer, replace the number by the sum of the squares of its digits, and repeat the process un…

Insertion Sort List Sort a linked list using insertion sort. leetcode subject思路:标准的插入排序.考察一下链表的操作. 对链表进行插入排序的正确方法是:新建一个头节点,遍历原来的链表,对原链表的每个节点找到新链表中适合插入位置的前指针,然后执行插入操作.这种操作链表的题的技巧是:新建一个dummy作为head node,然后把数据插入到dummy的链表中,最后返回dummy.next. 链表的插入排序图示: 注意头结点…

题目描述 假设 LeetCode 即将开始其 IPO.为了以更高的价格将股票卖给风险投资公司,LeetCode希望在 IPO 之前开展一些项目以增加其资本. 由于资源有限,它只能在 IPO 之前完成最多 k 个不同的项目.帮助 LeetCode 设计完成最多 k 个不同项目后得到最大总资本的方式. 给定若干个项目.对于每个项目 i,它都有一个纯利润 Pi,并且需要最小的资本 Ci 来启动相应的项目.最初,你有 W 资本.当你完成一个项目时,你将获得纯利润,且利润将被添加到你的总资本中. 总而言之…

题目一:Combinations Given two integers n and k, return all possible combinations of k numbers out of 1 ... n. For example, If n = 4 and k = 2, a solution is: [ [2,4], [3,4], [2,3], [1,2], [1,3], [1,4], ] 分析: 题意给我们一个数字n, 和一个数字k,让我们求出从 1~~n中取出k个数所能得到的组合数…

1. Minimum Window Substring Given a string S and a string T, find the minimum window in S which will contain all the characters in T in complexity O(n). Example: Input: S = "ADOBECODEBANC", T = "ABC" Output: "BANC" Note: If t…

Given s1, s2, s3, find whether s3 is formed by the interleaving of s1 and s2. Example 1: Input: s1 = "aabcc", s2 = "dbbca", s3 = "aadbbcbcac" Output: true Example 2: Input: s1 = "aabcc", s2 = "dbbca", s3 =…

1. N-Queens The n-queens puzzle is the problem of placing n queens on an n×n chessboard such that no two queens attack each other. Given an integer n, return all distinct solutions to the n-queens puzzle. Each solution contains a distinct board confi…

Given n non-negative integers representing an elevation map where the width of each bar is 1, compute how much water it is able to trap after raining. The above elevation map is represented by array [0,1,0,2,1,0,1,3,2,1,2,1]. In this case, 6 units of…

1. Reverse Nodes in k-Group Given a linked list, reverse the nodes of a linked list k at a time and return its modified list. k is a positive integer and is less than or equal to the length of the linked list. If the number of nodes is not a multiple…

1. Linked List Cycle II Given a linked list, return the node where the cycle begins. If there is no cycle, return null. Note: Do not modify the linked list. 思路:想法是利用两指针,一个每次移动一步,另一个每次移动两步,如果存在环则这两个指针一定会相遇(这里可以在纸上画一下,因为后一个指针移动比前一个指针快,当后一个指针在环中来到前一个指针的…

1. Convert Sorted List to Binary Search Tree Given a singly linked list where elements are sorted in ascending order, convert it to a height balanced BST. For this problem, a height-balanced binary tree is defined as a binary tree in which the depth…

1. Unique Binary Search Trees Given n, how many structurally unique BST's (binary search trees) that store values 1...n? For example,Given n = 3, there are a total of 5 unique BST's. 1 3 3 2 1 \ / / / \ \ 3 2 1 1 3 2 / / \ \ 2 1 2 3 思路:和 Unique Binar…

1. Word Search Given a 2D board and a word, find if the word exists in the grid. The word can be constructed from letters of sequentially adjacent cell, where "adjacent" cells are those horizontally or vertically neighboring. The same letter cel…

1. Rotate List Given a list, rotate the list to the right by k places, where k is non-negative. Example: Given 1->2->3->4->5->NULL and k = 2, return 4->5->1->2->3->NULL. 思路:这题感觉有点没有说清楚,如果k大于了链表长度该怎么办呢?这个时候怎么确定旋转位置呢?从右往左数,超出数组…

1. Group Anagrams Given an array of strings, group anagrams together. For example, given: ["eat", "tea", "tan", "ate", "nat", "bat"], [ ["ate", "eat","tea"], ["…

1. Permutations Given a collection of distinct numbers, return all possible permutations. For example,[1,2,3] have the following permutations: [ [1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], [3,2,1] ]  思路:直接使用递归来遍历即可,因为数字是不重复的所以,所以这里的每层递归都从索引0开始遍历整个数组…