Java - 백준 코딩테스트 1157번 [문자열 - 단어 공부]

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
 
public class StudyWord {
 
    public static void main(String[] args) throws IOException {
        // 20210625 - 1157번
        ///////////////////////////////////////////////////////////////////////이해 못함 다시 풀기
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
        
        String str = br.readLine().toUpperCase();
        /*
        char arr[] = new char[str.length()];
        
        for (int i = 0; i < arr.length; i++) {
            arr[i] = str.charAt(i);
        }
        */
        int arr[] = new int[26];
        
        int max = -1;
        char result = '?';
        
        for (int i = 0; i < str.length(); i++) {
            arr[str.charAt(i) - 65]++;
            if (max < arr[str.charAt(i) - 65]) {
                max = arr[str.charAt(i) - 65];
                result = str.charAt(i);
            } else if (max == arr[str.charAt(i) - 65]) {
                result = '?';
            }
        }
 
        bw.write(String.valueOf(result));
        bw.flush();
        bw.close();
        br.close();
    }
 
}