Leetcode: 202. Happy Number
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:
Input: 19
Output: true
Explanation:
1^2 + 9^2 = 82
8^2 + 2^2 = 68
6^2 + 8^2 = 100
1^2 + 0^2 + 0^2 = 1
Solution:
class Solution {
public boolean isHappy(int n) {
if(n == 1) return true;
int num = n, sum = 0;
Set<Integer> checkLoopSet = new HashSet<>();
while(num != 1 && num > 0){
sum = 0;
while(num > 0){
sum += Math.pow((num % 10), 2);
num /= 10;
}
if(checkLoopSet.contains(sum))
return false;
else
checkLoopSet.add(sum);
num = sum;
}
return true;
}
}
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