Happy Number

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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

class Solution {
public:
    bool isHappy(int n) {
        if(n<=0){
            return false;
        }
        unordered_set<int> uset;
        int squareSum = 0;
        while(squareSum!=1){
            squareSum = 0;
            while(n){
                squareSum += (n%10)*(n%10);
                n /= 10;
            }
            n = squareSum ;
            if(uset.find(n)!=uset.end()){
                return false;
            }
            uset.insert(n);
        }
        return true;
    }
};

Happy Number

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原文地址：http://www.cnblogs.com/zengzy/p/5002290.html