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public class HappyNumber {
public boolean isHappy(int n) {
if (n < 1) {
return false;
}
Set<Integer> set = new HashSet<Integer>();
int result = n;
while (true) {
result = calc(result);
if (result == 1) {
return true;
}
if (set.contains(result)) {
return false;
}
set.add(result);
}
}
private int calc(int n) {
int result = 0;
while (n > 0) {
int x = n % 10;
n /= 10;
result += x * x;
}
return result;
}
}
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