LeetCode-in-Java
202. Happy Number
Easy
Write an algorithm to determine if a number n 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.
- 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.
Return true if n is a happy number, and false if not.
Example 1:
Input: n = 19
Output: true
Explanation:
12 + 92 = 82
82 + 22 = 68
62 + 82 = 100
12 + 02 + 02 = 1
Example 2:
Input: n = 2
Output: false
Constraints:
1 <= n <= 231 - 1
Solution
public class Solution {
public boolean isHappy(int n) {
boolean happy;
int a = n;
int rem;
int sum = 0;
if (a == 1 || a == 7) {
happy = true;
} else if (a > 1 && a < 10) {
happy = false;
} else {
while (a != 0) {
rem = a % 10;
sum = sum + (rem * rem);
a = a / 10;
}
if (sum != 1) {
happy = isHappy(sum);
} else {
happy = true;
}
}
return happy;
}
}