_202.java

package com.fishercoder.solutions;

import java.util.HashSet;
import java.util.Set;
/**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*/
public class _202 {

    public static boolean isHappy(int n) {
        if (n == 1) {
            return true;
        }
        Set<Integer> set = new HashSet();
        while (n != 1) {
            String str = String.valueOf(n);
            n = 0;
            for (int i = 0; i < str.length(); i++) {
                int temp = Character.getNumericValue(str.charAt(i));
                n += temp * temp;
            }
            if (n == 1) {
                return true;
            }
            if (!set.add(n)) {
                return false;
            }
        }
        return false;
    }


    public static void main(String... strings) {
        int n = 7;
        System.out.println(isHappy(n));
    }
}