Description：
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
public class Solution {
public boolean isHappy(int n) {
ArrayList<String> tList = new ArrayList<>();
String sn = new String(n+"");
while(true) {
String t = calcu(sn);
if(t.equals("1")) {
return true;
}
if(tList.contains(t)) {
return false;
}
tList.add(t);
sn = t;
}
}
public static String calcu(String str) {
int t = 0;
for(int i=0; i<str.length(); i++) {
t += Integer.parseInt(str.charAt(i)+"") * Integer.parseInt(str.charAt(i)+"");
}
return new String(t+"");
}
}