202. Happy Number
Write an algorithm to determine if a number is “happy”. A happy number is a number defin…
258. Add Digits
Given a non-negative integer num, repeatedly add all its digits until the result has only one digit.…
441. Arranging Coins
You have a total of n coins that you want to form in a staircase shape, where every k-th row must ha…
168. Excel Sheet Column Title
Given a positive integer, return its corresponding column title as appear in an Excel sheet. For exa…
231. Power of Two
Given an integer, write a function to determine if it is a power of two. class Solution { public boo…
263. Ugly Number
Write a program to check whether a given number is an ugly number. Ugly numbers are positive numbers…
507. Perfect Number
We define the Perfect Number is a positive integer that is equal to the sum of all its positive divi…
172. Factorial Trailing Zeroes
Given an integer n, return the number of trailing zeroes in n!. Note: Your solution should be in log…
171. Excel Sheet Column Number
Related to question Excel Sheet Column Title Given a column title as appear in an Excel sheet, retur…
633. Sum of Square Numbers
Given a non-negative integer c, your task is to decide whether there’re two integers a and b s…