LC-(E)-Happy Number.cpp

// Write an algorithm to determine if a number n 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.
// 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.
// Return true if n is a happy number, and false if not.



class Solution {
public:
    bool isHappy(int n) {

        set<int> st;
        
        while(true){
            int x=0;
            while(n!=0){
            x+=(n%10) * (n%10);
            n/=10;
        }

        if(x==1) return true;

        if(st.find(x)!=st.end()) return false;

        st.insert(x);
        n=x;

        }
        
    }
};