sunwill的博客

原题： 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 with another

【题目】 Given an array of strings, group anagrams together.For example, given: [“eat”, “tea”, “tan”, “ate”, “nat”, “bat”], Return: [ [“ate”, “eat”,”tea”], [“nat”,”tan”], [“bat”] ]【分析】题意为将字符串数组中

原题： Given a set of distinct positive integers, find the largest subset such that every pair (Si, Sj) of elements in this subset satisfies: Si % Sj = 0 or Sj % Si = 0.If there are multiple solutions, r

原题： We are playing the Guess Game. The game is as follows:I pick a number from 1 to n. You have to guess which number I picked.Every time you guess wrong, I’ll tell you whether the number I picked is

原题： All DNA is composed of a series of nucleotides abbreviated as A, C, G, and T, for example: “ACGAATTCCG”. When studying DNA, it is sometimes useful to identify repeated sequences within the DNA.Wr

原题： Given a string array words, find the maximum value of length(word[i]) * length(word[j]) where the two words do not share common letters. You may assume that each word will contain only lower case

原题： Given a set of distinct integers, nums, return all possible subsets.Note: The solution set must not contain duplicate subsets.For example, If nums = [1,2,3], a solution is: [ [3], [1], [2

原题: Given an array of citations (each citation is a non-negative integer) of a researcher, write a function to compute the researcher’s h-index.According to the definition of h-index on Wikipedia: “A

原题： Given a collection of integers that might contain duplicates, nums, return all possible subsets.Note: The solution set must not contain duplicate subsets.For example, If nums = [1,2,2], a solutio

原题： Evaluate the value of an arithmetic expression in Reverse Polish Notation.Valid operators are +, -, *, /. Each operand may be an integer or another expression.Some examples: [“2”, “1”, “+”, “3”,

【原题】 Given a 2d grid map of ‘1’s (land) and ‘0’s (water), count the number of islands. An island is surrounded by water and is formed by connecting adjacent lands horizontally or vertically. You may a

Given a string that contains only digits 0-9 and a target value,return all possibilities to add binary operators (not unary) +, -, or * between the digits so they evaluate to the target value. Examples

【原题】 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.Ea

【原题】 Follow up for N-Queens problem. Now, instead outputting board configurations, return the total number of distinct solutions.【分析】 本题为N皇后问题，要求解的个数 思路是回溯法，一行一行地遍历，每个位置试一下，看能否构成解。 由题目要求，同一行、同一列

原题： Given an array of non-negative integers, you are initially positioned at the first index of the array.Each element in the array represents your maximum jump length at that position.Your goal is to

原题： Given a string which contains only lowercase letters, remove duplicate letters so that every letter appear once and only once. You must make sure your result is the smallest in lexicographical ord

【题目】 Implement a trie with insert, search, and startsWith methods.Note: You may assume that all inputs are consist of lowercase letters a-z. 【解析】 题目要求实现Prefix Tree(前缀树)的insert、search和startWith方法，所以

原题： Given a non-empty array of integers, return the k most frequent elements. For example, Given [1,1,1,2,2,3] and k = 2, return [1,2].Note:You may assume k is always valid, 1 ≤ k ≤ number of unique

原题： Given a non negative integer number num. For every numbers i in the range 0 ≤ i ≤ num calculate the number of 1’s in their binary representation and return them as an array.Example: For num = 5 y

原题： 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” i

原题： 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,null,null,15,7] 3

原题：Given an unsorted integer array, find the first missing positive integer.For example, Given [1,2,0] return 3, and [3,4,-1,1] return 2.Your algorithm should run in O(n) time and uses constant space

原题：Count the number of prime numbers less than a non-negative number, n.求小于正整数n的质数的个数通常我们的做法是从最小的质数2开始遍历直到n，判断其中每一个数是否为质数，当n很大的时候，肯定超时。有更高效的解法如下：质数只能被1和他自己整除，也就是说他不包含基本因子2,3,5,7等我们可以排除上述这些数来大大提高遍历效率2是最

原题：Given an array of integers, every element appears twice except for one. Find that single one.Note:Your algorithm should have a linear runtime complexity. Could you implement it without usin

原题：Write a function that takes a string as input and reverse only the vowels of a string.Example 1:Given s = "hello", return "holle".Example 2:Given s = "leetcode", return "leotcede". 

原题： Given a pattern and a string str, find if str follows the same pattern.Here follow means a full match, such that there is a bijection between a letter in pattern and a non-empty word in str.Exampl

原题： 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:Digit strin

原题： Given a set of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T.The same repeated number may be chosen from C unlimited number

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],

**【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()

【原题】 Given an array which consists of non-negative integers and an integer m, you can split the array into m non-empty continuous subarrays. Write an algorithm to minimize the largest sum among these