202. Happy Number
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:
Input: 19 Output: true Explanation: 12 + 92 = 82 82 + 22 = 68 62 + 82 = 100 12 + 02 + 02 = 1
package leetcode.easy;
public class HappyNumber {
public boolean isHappy(int n) {
if (n == 0) {
return false;
}
while (n != 1) {
int n2 = n;
n = 0;
while (n2 > 0) {
n += (n2 % 10) * (n2 % 10);
n2 /= 10;
}
if (n == 4) {
return false;
}
}
return true;
}
@org.junit.Test
public void test() {
System.out.println(isHappy(19));
}
}