Happy number

gistfile1.cpp

/*
https://leetcode.com/problems/happy-number/

For cycle detection:
1. Floyd's tortoise and rabbit algorithm (two pointers; slow and fast)
2. Brant's algorithm
3. using Hash table to detect duplicated values;
*/

class Solution {
public:
    bool isHappy(int n) {
       int slow = n, fast = n;
       
       do {
           slow = sumSquare(slow);
           fast = sumSquare(sumSquare(fast));
       } while(slow != fast);
       
       
       if(slow == 1) {
        
           return true;
       }
       
       return false;
    }
    
    int sumSquare(int n) {
        int sum = 0;
        
        while(n) {
            int temp = n % 10;
            sum += temp*temp;
            n /= 10;
        }
        
        return sum;
    }
};