202.Happy number.cpp

202. Happy Number
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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.

 

Example 1:

Input: n = 19
Output: true
Explanation:
12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1
Example 2:

Input: n = 2
Output: false
 

Constraints:

1 <= n <= 231 - 1
  
  
 //Solution 
  //langage : C++
  class Solution {
public:
    bool isHappy(int n) {
        int tmp = 0;
        set<int> visited;
        
        while(true){
            tmp = 0;
            while(n > 0){
                tmp += pow((n%10), 2);
                n/=10;
            }
            n = tmp;
            if(n == 1){
                break;
            }else if(visited.find(n)!=visited.end()){
                return false;
            }
            visited.insert(n);
        }
        return true;
    }
};