原创 【leetcode】24. Swap Nodes in Pairs
Given a linked list, swap every two adjacent nodes and return its head. You may not modify the values in the list's nod
原创 【leetcode】25. 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 integ
原创 【leetcode】383. Ransom Note
Given an arbitrary ransom note string and another string containing letters from all the magazines, write a function th
原创 【leetcode】263. Ugly Number
Write a program to check whether a given number is an ugly number. Ugly numbers are positive numbers whose prime factor
原创 【leetcode】204. Count Primes
Count the number of prime numbers less than a non-negative number, n. Example: Input: 10 Output: 4 Explanation: There
原创 【leetcode】240. Search a 2D Matrix II
Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties: In
原创 【leetcode】894. All Possible Full Binary Trees
A full binary tree is a binary tree where each node has exactly 0 or 2 children. Return a list of all possible full bin
原创 【leetcode】513. Find Bottom Left Tree Value
Given a binary tree, find the leftmost value in the last row of the tree. Example 1: Input: 2 / \ 1 3 Out
原创 【leetcode】515. Find Largest Value in Each Tree Row
You need to find the largest value in each row of a binary tree. Example: Input: 1 / \ 3
原创 【leetcode】779. K-th Symbol in Grammar
On the first row, we write a 0. Now in every subsequent row, we look at the previous row and replace each occurrence of
原创 【leetcode】77. Combinations
Given two integers n and k, return all possible combinations of k numbers out of 1 ... n. Example: Input: n = 4, k = 2
原创 【leetcode】3. Longest Substring Without Repeating Characters
Given a string, find the length of the longest substring without repeating characters. Example 1: Input: "abcabcbb" Ou
原创 【leetcode】48. Rotate Image
You are given an n x n 2D matrix representing an image. Rotate the image by 90 degrees (clockwise). Note: You have to r
原创 【leetcode】784. Letter Case Permutation
Given a string S, we can transform every letter individually to be lowercase or uppercase to create another string. Re
原创 229. Majority Element II
Given an integer array of size n, find all elements that appear more than ⌊ n/3 ⌋ times. Note: The algorithm should run