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

// Author : Hao Chen

// Date : 2015-06-08

/**********************************************************************************

*

* 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

*

* 1^2 + 9^2 = 82

* 8^2 + 2^2 = 68

* 6^2 + 8^2 = 100

* 1^2 + 0^2 + 0^2 = 1

*

* Credits:Special thanks to @mithmatt and @ts for adding this problem and creating all test cases.

*

**********************************************************************************/

#include <stdlib.h>

#include <iostream>

#include <map>

using namespace std;

int squares(int n) {

int result = 0;

int sq = 0;

for (; n>0; n/=10) {

sq = n%10;

result += (sq * sq);

}

return result;

}

bool isHappy(int n) {

if (n==1) return true;

map<int, bool> m;

m[n]=true;

while (n!=1) {

n = squares(n);

//cout << n << endl;

if (m.find(n) != m.end()){

return false;

}

m[n] = true;

}

return true;

}

int main(int argc, char** argv)

{

int n = 2;

if (argc > 1){

n = atoi(argv[1]);

}

cout << n << (isHappy(n) ? " is " : " isn't ") << "a happy number" << endl;

return 0;

}