James Pan

原题网址：https://leetcode.com/problems/strobogrammatic-number-ii/ A strobogrammatic number is a number that looks the same when rotated 180 degrees (looked at upside down). Find all strobogrammati

原题网址：https://leetcode.com/problems/reverse-integer/ Reverse digits of an integer. Example1: x = 123, return 321 Example2: x = -123, return -321 click to show spoilers. Have you thought

原题网址：https://leetcode.com/problems/integer-to-roman/ Given an integer, convert it to a roman numeral. Input is guaranteed to be within the range from 1 to 3999. 方法：理解罗马数字的规律。二分法。 public clas

原题网址：https://leetcode.com/problems/roman-to-integer/ Given a roman numeral, convert it to an integer. Input is guaranteed to be within the range from 1 to 3999. 方法：理解罗马数字。 public class Solut

原题网址：https://leetcode.com/problems/count-and-say/ The count-and-say sequence is the sequence of integers beginning as follows: 1, 11, 21, 1211, 111221, ... 1 is read off as "one 1" or 11.

原题网址：https://leetcode.com/problems/multiply-strings/ Given two numbers represented as strings, return multiplication of the numbers as a string. Note: The numbers can be arbitrarily large

原题网址：https://leetcode.com/problems/restore-ip-addresses/ Given a string containing only digits, restore it by returning all possible valid IP address combinations. For example: Given "2552551

原题网址：https://leetcode.com/problems/number-of-digit-one/ Given an integer n, count the total number of digit 1 appearing in all non-negative integers less than or equal to n. For example: Give

原题网址：https://leetcode.com/problems/valid-number/ Validate if a given string is numeric. Some examples: "0" => true " 0.1 " => true "abc" => false "1 a" => false "2e10" => true Note:

原题网址：https://leetcode.com/problems/count-primes/ Description: Count the number of prime numbers less than a non-negative number, n. Credits: Special thanks to @mithmatt for adding this pro

原题网址：https://leetcode.com/problems/happy-number/ 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

原题网址：https://leetcode.com/problems/additive-number/ Additive number is a string whose digits can form additive sequence. A valid additive sequence should contain at least three numbers. Except

原题网址：https://leetcode.com/problems/move-zeroes/ Given an array nums, write a function to move all 0's to the end of it while maintaining the relative order of the non-zero elements. For exam

原题网址：https://leetcode.com/problems/add-digits/ Given a non-negative integer num, repeatedly add all its digits until the result has only one digit. For example: Given num = 38, the proces

原题网址：https://leetcode.com/problems/largest-number/ Given a list of non negative integers, arrange them such that they form the largest number. For example, given [3, 30, 34, 5, 9], the largest

原题网址：https://leetcode.com/problems/factorial-trailing-zeroes/ Given an integer n, return the number of trailing zeroes in n!. Note: Your solution should be in logarithmic time complexity. 方法：

原题网址：https://leetcode.com/problems/integer-to-english-words/ Convert a non-negative integer to its english words representation. Given input is guaranteed to be less than 231 - 1. For example,

原题网址：https://leetcode.com/problems/bulls-and-cows/ You are playing the following Bulls and Cows game with your friend: You write down a number and ask your friend to guess what the number is. E

原题网址：https://leetcode.com/problems/sum-root-to-leaf-numbers/ Given a binary tree containing digits from 0-9 only, each root-to-leaf path could represent a number. An example is the root-to-l

原题网址：https://leetcode.com/problems/longest-consecutive-sequence/ Given an unsorted array of integers, find the length of the longest consecutive elements sequence. For example, Given [100, 4,

原题网址：https://leetcode.com/problems/super-ugly-number/ Write a program to find the nth super ugly number. Super ugly numbers are positive numbers whose all prime factors are in the given prime