problem0202

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202. Happy Number

题目

Write an algorithm to determine if a number is "happy".

A happy number is a number defined by the following process:

1. Starting with any positive integer, replace the number by the sum of the squares of its digits,
2. and repeat the process until the number equals 1 (where it will stay), or it loops endlessly in a cycle which does not include 1. Those numbers for which this process ends in 1 are happy numbers.

Example: 19 is a happy number

1^2 + 9^2 = 82
8^2 + 2^2 = 68
6^2 + 8^2 = 100
1^2 + 0^2 + 0^2 = 1

Credits:Special thanks to @mithmatt and @ts for adding this problem and creating all test cases.

解题思路

见程序注释