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