leetcode 202. Happy Number

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本文介绍了一种用于判断一个正整数是否为快乐数的算法。快乐数是指通过反复替换该数为它每个位数的平方和，最终得到1的数。文章提供了使用C++实现的具体代码示例。

202. 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 integer, replace the number by the sum of the squares of its digits, 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

12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1

用map来存出现过的数

class Solution {
public:
    bool isHappy(int n) 
    {
        map<int,int> p;
        while (n != 1 && p.find(n) == p.end())  
        {
            int sum = 0;
            p[n] ++;  
            while (n != 0)
            {
                sum += pow(n % 10, 2); 
                n /= 10;
            }
            n = sum;
        }
        return n==1;   
    }
};