Happy number of Leetcode

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 and replace the number by the Sum of the squares of its digits, and repeat the process until the number equals 1 (where it would stay), or it loops Endl essly in a cycle which does not include 1. Those numbers for which this process ends in 1 is happy numbers.

Example:19 is a happy number

• 12 + 92 = 82
• 82 + 22 = 68
• 62 + 82 = 100
• 12 + 02 + 02 = 1

This problem is very simple, the idea is roughly the following, first take this number of each digit, and then consider that the termination condition is 1 or cycle

At first, the final condition was judged to be the end of the 1, forgetting that if the infinite loop would happen, then there would be no AC.

From the Internet to find a bit of information, found that using hashset is more reasonable, the first add () method will not be in the collection of elements, followed by the contain () method will determine whether a number is within the collection,

So write two functions, one is to get the next number to judge, and the other is to judge if the number is happy.

The code is as follows:

public class Solution {public    boolean ishappy (int n) {        hashset<integer> hash = new Hashset<integer> ( );        while (n! = 1) {            if (Hash.contains (n)) {                return false;            }            Hash.add (n);            n = s (n);        }        return true;    }    public int s (int n) {int num = 0;        while (n!=0) {        int u = N/10;        int v = n%10;        n = u;        num + = v*v;        }        int result = num;        return result;}}

　　

Happy number of Leetcode