👨‍💻 Map / toLowerCase/charAt/getOrDefault/Map.Entry/entrySet

문제 : 

알파벳 대소문자로 된 단어가 주어지면, 이 단어에서 가장 많이 사용된 알파벳이 무엇인지 알아내는 프로그램을 작성하시오. 단, 대문자와 소문자를 구분하지 않는다.

 

나의 답 : 

import java.util.*;

public class Main {
    public static void main(String[] args) {

        Scanner s = new Scanner(System.in);

        String line= s.nextLine().toUpperCase();

        HashMap<Character,Integer> count= new HashMap<>();

        for(int i=0; i<line.length();i++){
            char c=line.charAt(i);
            count.put(c,count.getOrDefault(c,0)+1);
        }

        char mostCommon = ' ';
        int mostCount=0;
        for(Map.Entry<Character,Integer> entry : count.entrySet()){
            if(entry.getValue()>mostCount){
                mostCommon=entry.getKey();
                mostCount=entry.getValue();
            }
        }

        int check=0;
        for(Map.Entry<Character,Integer> entry : count.entrySet()) {
            if (entry.getValue() == mostCount) {
                check++;
            }
        }
        if(check>1) System.out.println("?");
        else System.out.println(mostCommon);


    }
}

 

메모리 축소 버전 :  HashMap -> 배열

 

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner s = new Scanner(System.in);
        String line = s.nextLine().toUpperCase();
        
        int[] count = new int[26]; // 알파벳 개수만큼 배열 생성
        
        for (char c : line.toCharArray()) {
            if (Character.isAlphabetic(c)) { // 알파벳인 경우에만 처리
                count[c - 'A']++;
            }
        }

        int maxCount = 0;
        char mostCommon = ' ';
        boolean isUnique = true;
        
        for (int i = 0; i < 26; i++) {
            if (count[i] > maxCount) {
                maxCount = count[i];
                mostCommon = (char) (i + 'A');
                isUnique = true;
            } else if (count[i] == maxCount) {
                isUnique = false;
            }
        }
        
        if (isUnique) {
            System.out.println(mostCommon);
        } else {
            System.out.println("?");
        }
    }
}