李晓磊-CSDN博客

原创【LeetCode】141. Linked List Cycle

问题Given a linked list, determine if it has a cycle in it.To represent a cycle in the given linked list, we use an integer pos which represents the position (0-indexed) in the linked list where tail ...

2018-12-09 10:38:42 113

原创【LeetCode】136. Single Number

【LeetCode】136. Single Number 问题思路常规解法基于比特操作的解法知识点比特位操作问题Given a non-empty array of integers, every element appears twice except for one. Find that single one.Note:Your algorithm should have a line...

2018-12-09 09:18:12 128

原创【LeetCode】017.Letter Combinations of a Phone Number

题目：Given a digit string, return all possible letter combinations that the number could represent.A mapping of digit to letters (just like on the telephone buttons) is given below.Input

2015-07-03 13:10:42 323 1

原创【LeetCode】016.3Sum Closest

题目：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 hav

2015-07-03 13:07:47 290

原创【LeetCode】015.3Sum

题目：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 tripl

2015-05-20 22:12:55 341

原创【LeetCode】012.Integer to Roman

题目：Given an integer, convert it to a roman numeral.Input is guaranteed to be within the range from 1 to 3999.解答：从千位到个位，根据位数不同选择不同的字母，char1,char5,char10分别代表该位表示1，5和10的字母。c为当前位数字（0---9），

2015-05-20 12:25:56 315

原创【LeetCode】011.Container With Most Water

题目：Given n non-negative integers a1, a2, ..., an, where each represents a point at coordinate (i, ai). n vertical lines are drawn such that the two endpoints of line i is at (i, ai) and (i,

2015-05-20 11:30:16 277

原创【LeetCode】005.Longest Palindromic Substring

题目：Given a string S, find the longest palindromic substring in S. You may assume that the maximum length of S is 1000, and there exists one unique longest palindromic substring.解答：典型动态规划

2015-05-19 22:34:35 276

原创【LeetCode】003.Longest Substring Without Repeating Characters

题目：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 length is

2015-05-19 19:29:05 374

原创【LeetCode】002.Add Two Numbers

题目：You are given two linked lists representing two non-negative numbers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it

2015-05-19 18:13:56 677

原创【LeetCode】001.Two Sum

题目：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 ta

2015-05-19 17:40:37 304

原创【LeetCode】206.reverse linked list

题目：Reverse a singly linked list.解答：关键是弄明白next到底指向哪个元素；代码：/** * Definition for singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode(int x) {

2015-05-11 22:20:58 215

原创【LeetCode】205.Isomorphic Strings

题目：Given two strings s and t, determine if they are isomorphic.Two strings are isomorphic if the characters in s can be replaced to get t.All occurrences of a character must be replaced

2015-05-11 21:35:36 345

原创【LeetCode】204.Count Primes

题目：Description:Count the number of prime numbers less than a non-negative number, nclick to show more hints.Credits:Special thanks to @mithmatt for adding this problem and creating

2015-05-11 21:00:22 263

原创【LeetCode】203.Remove Linked List Elements

题目：Remove all elements from a linked list of integers that have value val.ExampleGiven: 1 --> 2 --> 6 --> 3 --> 4 --> 5 --> 6, val = 6Return: 1 --> 2 --> 3 --> 4 --> 5解答：使用2个指针，一个指向当

2015-05-11 12:33:06 260

原创【LeetCode】202.happy number

题目：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 th

2015-05-11 12:11:41 287

原创【LeetCode】198.House Robber

题目：You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed, the only constraint stopping you from robbing each of them is that adjac

2015-05-11 11:40:19 267

原创【LeetCode】189.Rotate Array

题目：Rotate an array of n elements to the right by k steps.For example, with n = 7 and k = 3, the array [1,2,3,4,5,6,7] is rotated to [5,6,7,1,2,3,4].Note:Try to come up as many soluti

2015-05-08 09:14:54 328

原创【LeetCode】172.Factorial Trailing Zeroes

题目：Given an integer n, return the number of trailing zeroes in n!.Note: Your solution should be in logarithmic time complexity.解答：对n!进行质因数分解n!=2^x * 3^y * 5^z * .....，容易看出，n!尾部零的数量

2015-05-07 18:58:04 264

原创【LeetCode】171.Excel Sheet Column Number

题目：Related to question Excel Sheet Column TitleGiven a column title as appear in an Excel sheet, return its corresponding column number.For example: A -> 1 B -> 2 C -> 3

2015-05-07 18:33:03 266

原创【LeetCode】168.Excel Sheet Column Title

题目:Given a positive integer, return its corresponding column title as appear in an Excel sheet.For example: 1 -> A 2 -> B 3 -> C ... 26 -> Z 27 -> AA 28 -> AB

2015-05-07 18:10:23 336

原创【LeetCode】165.Compare Version Numbers

题目：Compare two version numbers version1 and version2.If version1 > version2 return 1, if version1 version2 return -1, otherwise return 0.You may assume that the version strings are non-emp

2015-04-09 17:57:11 258

原创【LeetCode】160.Intersection of Two Linked Lists

题目：Write a program to find the node at which the intersection of two singly linked lists begins.For example, the following two linked lists:A: a1 → a2 ↘

2015-04-09 16:59:57 281

原创【LeetCode】155.Min Stack

题目：Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.push(x) -- Push element x onto stack.pop() -- Removes the element on top of the stack.top(

2015-04-09 12:51:54 249

原创【LeetCode】125.Valid Palindrome

题目：Given a string, determine if it is a palindrome, considering only alphanumeric characters and ignoring cases.For example,"A man, a plan, a canal: Panama" is a palindrome."race a car"

2015-04-09 11:46:16 245

原创【LeetCode】119.Pascal Triangle II

题目：Given an index k, return the kth row of the Pascal's triangle.For example, given k = 3,Return [1,3,3,1].Note:Could you optimize your algorithm to use only O(k) extra space?解答：

2015-04-03 09:16:07 248

原创【LeetCode】118.Pascal's Triangle

题目：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]]解答：帕斯卡三角规律：从1开始

2015-04-02 18:44:24 236

原创【LeetCode】112.Path Sum

题目：Given a binary tree and a sum, determine if the tree has a root-to-leaf path such that adding up all the values along the path equals the given sum.For example:Given the below binary tree

2015-04-02 18:19:12 257

原创【LeetCode】111.Minimum Depth of Binary Tree

题目：Given a binary tree, find its minimum depth.The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.解答：数深度相关问题用递归方式很好解决，递归公式为

2015-04-02 17:56:48 229

原创【LeetCode】110.Balanced Binary Tree

题目：Given a binary tree, determine if it is height-balanced.For this problem, a height-balanced binary tree is defined as a binary tree in which the depth of the two subtrees of every node ne

2015-04-01 10:29:35 235

原创【LeetCode】107.Binary Tree Level Order Traversal II

题目：Given a binary tree, return the bottom-up level order traversal of its nodes' values. (ie, from left to right, level by level from leaf to root).For example:Given binary tree {3,9,20,#,

2015-03-31 15:51:11 277

原创【LeetCode】104.Maximum Depth of Binary Tree

题目：Given a binary tree, find its maximum depth.The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.解答：用的土方法，水平遍历，每次装入时带上层级信息

2015-03-31 15:08:29 373

原创【LeetCode】102.Binary Tree Level Traversal

题目：Given a binary tree, return the level order traversal of its nodes' values. (ie, from left to right, level by level).For example:Given binary tree {3,9,20,#,#,15,7}, 3 / \ 9

2015-03-31 14:34:41 229

原创【LeetCode】101.Symmetric Tree

题目：Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).For example, this binary tree is symmetric: 1 / \ 2 2 / \ / \3 4 4 3

2015-03-31 12:24:43 273

原创【LeetCode】100.Same Tree

题目：Given two binary trees, write a function to check if they are equal or not.Two binary trees are considered equal if they are structurally identical and the nodes have the same value.解答：

2015-03-31 12:06:52 227

原创【LeetCode】088.Merge Sorted Array

题目：Given two sorted integer arrays A and B, merge B into A as one sorted array.Note:You may assume that A has enough space (size that is greater or equal to m + n) to hold additional eleme

2015-03-30 16:24:12 223

原创【LeetCode】083.Remove Duplicates from Sorted List

题目：Given a sorted linked list, delete all duplicates such that each element appear only once.For example,Given 1->1->2, return 1->2.Given 1->1->2->3->3, return 1->2->3.解答：类似单链表的遍历。需要

2015-03-30 15:48:36 315

原创【LeetCode】070.Climbing Staris

题目：You are climbing a stair case. It takes n steps to reach to the top.Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?解答：基础级的递归题，公式为f(n) =

2015-03-30 15:28:41 333

原创【LeetCode】066.Add Binary

题目：Given two binary strings, return their sum (also a binary string).For example,a = "11"b = "1"Return "100".解答：从后往前遍历计算即可，注意进位的情况，尤其是最高位的进位。Tips：Java中String 和 char[]的互相转换：Stri

2015-03-30 14:50:00 243

原创【LeetCode】066.Plus One

题目：Given a non-negative number represented as an array of digits, plus one to the number.The digits are stored such that the most significant digit is at the head of the list.解答：考虑进位问题，从

2015-03-27 16:18:40 256

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