369 games (with.Java)

This article looks into the “369 Game” issue.

As I solve coding test problems, I look back on the problems I solved and look into different solution methods to learn more.

Let’s look at the problem first.

problem

I’m playing 369 games with my shy friends.

The 369 game is a game in which the numbers are numbered one by one starting from 1, and for numbers containing 3, 6, or 9, clapping as much as the number of 3, 6, or 9 is used instead of the number.

Complete the solution function so that when the number order that the mush must speak is given as a parameter, it returns the number of times the mush must clap.

Restrictions

• 1 ≤ order ≤ 1,000,000

Input/Output Example

My solution to the problem

import java.util.*;
class Solution {
     public int solution(int order) {
         int answer = 0;

         for(char str : Integer.toString(order).toCharArray()){
             int temp = str - '0';
             if(temp - 3 == 0 || temp - 6 == 0 || temp - 9 == 0){
                 answer++;
             }
         }
         return answer;
     }
}

Solution explanation

The reason for subtracting ‘0’ from int temp = str - ‘0’; is to convert a character number to an integer type.

Character numbers are expressed as ASCII code values, and the ASCII code value of the number ‘0’ is 48.

Therefore, you can convert a character number to an integer by subtracting ‘0’ and the character number.

For example, if str is ‘3’, ‘3’ - ‘0’ evaluates to 51 - 48. This will have the same value as the integer number 3.

In other words, int temp = str - ‘0’; converts a character number to an integer.