Title: Valid Anagram Source: leetcode.com Given two strings s and t, write a function to determine if t is an anagram of s. For example, s = “anagram”, t = “nagaram”, return true. s = “rat”, t = “car”, return false. Note: You may assume the string contains only lowercase alphabets. Follow up: What if ...

Title: Unique Paths II Source: leetcode.com Follow up for “Unique Paths”: Now consider if some obstacles are added to the grids. How many unique paths would there be? An obstacle and empty space is marked as 1 and 0 respectively in the grid. For example, There is one obstacle in the middle of a 3×3 ...

Title: Unique Paths Source: leetcode.com A robot is located at the top-left corner of a m x n grid (marked ‘Start’ in the diagram below). The robot can only move either down or right at any point in time. The robot is trying to reach the bottom-right corner of the grid (marked ‘Finish’ in the ...

Title: Unique Binary Search Trees Source: leetcode.com 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 / / \ ...

Title: Ugly Number II Source: leetcode.com Write a program to find the n-th ugly number. Ugly numbers are positive numbers whose prime factors only include 2, 3, 5. For example, 1, 2, 3, 4, 5, 6, 8, 9, 10, 12 is the sequence of the first 10 ugly numbers. Note that 1 is typically treated ...

Title: Sudoku Solver Source: leetcode.com Write a program to solve a Sudoku puzzle by filling the empty cells. Empty cells are indicated by the character '.'. You may assume that there will be only one unique solution. Java solution Java /* https://leetcode.com/problems/sudoku-solver/ */ class SudokuSolver { public void solveSudoku(char[][] board) { int N = board.length; ...

Title: Sort Colors Source: leetcode.com Given an array with n objects colored red, white or blue, sort them so that objects of the same color are adjacent, with the colors in the order red, white and blue. Here, we will use the integers 0, 1, and 2 to represent the color red, white, and blue ...

Title: Single Number III Source: leetcode.com Given an array of numbers nums, in which exactly two elements appear only once and all the other elements appear exactly twice. Find the two elements that appear only once. For example: Given nums = [1, 2, 1, 3, 2, 5], return [3, 5]. Note: The order of the ...

Title: Search a 2D Matrix II Source: leetcode.com Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties: Integers in each row are sorted in ascending from left to right. Integers in each column are sorted in ascending from top to bottom. For example, ...