202. Happy Number

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Total Accepted: 54163
Total Submissions: 152329
Difficulty: Easy

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

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

Java:

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public class Solution {
    public boolean isHappy(int n) {
        while(n>6){
            int temp=0;
            while(n!=0){
                temp+=(n%10)*(n%10);
                n/=10;
            }
            n=temp;
        }
        return n==1;
    }
}

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