[leetcode]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

class Solution {public:    bool isHappy(int n) {        if(n<0)            return false;        if(n==1)            return true;        unordered_multiset<int> iset;        iset.insert(n);                while(true){            int s=0;            while(n){                s+=(n%10)*(n%10);                n/=10;            }            if(s==1)                return true;            else if(iset.count(s)==1)                return false;            n=s;            iset.insert(n);        }    }};