摘要：
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 integer... 阅读全文
摘要：
You are playing the following Bulls and Cows game with your friend: You write a 4-digit secret number and ask your friend to guess it. Each time your ... 阅读全文
摘要：
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... 阅读全文