- 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: **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.
public class Solution {
public boolean isHappy(int n) {
int cur = n;
if(n == 1) return true;
Set<Integer> intSet = new HashSet<>();
while(cur != 1 && cur > 0){
int sum = 0;
while(cur > 0){
int rem = cur % 10;
sum += rem*rem;
cur = cur/10;
}
if(sum == 1 ) return true;
if(intSet.contains(sum)) return false;
else intSet.add(sum);
cur = sum;
}
return true;
}
}
