백준(1157) JAVA - 단어 공부

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		
		Scanner sc = new Scanner(System.in);
		
		String str = sc.nextLine();
		char[] ar = str.toUpperCase().toCharArray();
		int[] num = new int[(int)'Z' + 1];
		
		for(int i = 0 ; i < str.length(); i++) {
			num[(int)ar[i]]++; 
		}
		int tmp = 0;
		int alpha = 0;
		int cnt = 0;
		for(int i = 0 ; i < (int)'Z'+1 ; i++) {
			if(num[i] != 0) {
				if(tmp < num[i]) {
					tmp = num[i];
					alpha = i;
				} 
			}
		}
		
		for(int i = 0 ; i < (int)'Z' + 1 ; i++) {
			if(tmp == num[i]) {
				cnt++;
			}
		}
		
		if(cnt < 2) {
			System.out.println((char)alpha);
		} else {
			System.out.println("?");
		}
	}
}