题目
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.
答案
class Solution {
public boolean isHappy(int n) {
Set<Integer> set = new HashSet<>();
set.add(n);
int sum = 0;
while(n != 1) {
sum = 0;
while(n > 0) {
int mod = n % 10;
n = n / 10;
sum += Math.pow(mod, 2);
}
if(set.contains(sum)) return false;
else set.add(sum);
n = sum;
}
return true;
}
}
