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: 19 is a happy number
- 12 + 92 = 82
- 82 + 22 = 68
- 62 + 82 = 100
- 12 + 02 + 02 = 1
没什么trick,找题目要求做即可.
public class Solution {
public boolean isHappy(int n) {
Set<Integer> set = new HashSet<>();
int next = n;
while (!set.contains(next)) {
set.add(next);
n = next;
next = 0;
while (n > 0) {
next += (n % 10) * (n % 10);
n /= 10;
}
if (next == 1) {
return true;
}
}
return false;
}
}