LeetCode 202 - Happy Number - 题解/Solution

https://leetcode.com/problems/happy-number/

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/**
* 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
*
* 1^2 + 9^2 = 82
* 8^2 + 2^2 = 68
* 6^2 + 8^2 = 100
* 1^2 + 0^2 + 0^2 = 1
*
* @author dongyuxi
*
*/
public class Solution {
public boolean isHappy(int n) {
if (n <= 0) {
return false;
}

Set<Integer> set = new HashSet<Integer>();
while (1 != n) {
int sum = 0;
while (n > 0) {
int digit = n % 10;
n = n / 10;
sum += digit * digit;
}
if (sum == 1) {
break;
}
if (set.contains(sum)) {
return false;
}
set.add(sum);
n = sum;
}
return true;
}
}


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