【LeetCode】202

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

Solution: 辅助函数；循环计算每位数字的平方和，直到出现结果为1(返回true)或者重复(返回false)

class Solution {
public:
    bool isHappy(int n) {
        map<int,bool> m;
        int ret=sum(n);
        while(ret!=1){
            if(m[ret]==true)return false;
            m[ret]=true;
            ret=sum(ret);
        }
        return true;
    }
    int sum(int n){
        int ret=0;
        while(n){
            ret += (n%10)*(n%10);   //不支持（n%10)^2
            n /= 10;
        }
        return ret;
    }
};