LeetCode:Happy Number

problem:

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:  同循环小数的计算

class Solution {
public:
    bool isHappy(int n) {
        unordered_set<int> markset;    //set存储已出现的数字    
        if(n<1) return false;
        if(n==1) return true;
        markset.insert(n);
        while(true)
        {
         int sum=0;
         while(n)
        {
            sum+=(n%10)*(n%10);
            n/=10;
        }
        if(sum==1)
            return true;
        else if(markset.find(sum)!=markset.end())
            return false;
        markset.insert(sum);
        n=sum;
         }
    }
};

原文：http://www.cnblogs.com/xiaoying1245970347/p/4609764.html