[프로그래머스][해시] 완주하지 못한 선수

https://programmers.co.kr/learn/courses/30/lessons/42576

코딩테스트 연습 - 완주하지 못한 선수

 

배열로 풀이 --> 실패

package com.company;

import java.util.ArrayList;
import java.util.Arrays;

public class programmers {

    public static void main(String[] args) {
     //https://programmers.co.kr/learn/courses/30/lessons/42576
        String[] participant = {"mislav", "stanko", "mislav", "ana"};
        String[] completion = {"stanko", "ana", "mislav"};
        String result = Solution.solution(participant,completion);
    }
    static class Solution {
        public static String solution(String[] participant, String[] completion) {
            String answer = "";
            //System.out.println(participant);// 출력: [Ljava.lang.String;@4554617c 못씀
            //Arrays.toString(participant);//출력: 글씨 안나옴
            //System.out.println(Arrays.toString(participant));// 정렬 전: [leo, kiki, eden]
            Arrays.sort(participant);// 정렬
            //System.out.println(Arrays.toString(participant));// 정렬 후: [eden, kiki, leo]
            Arrays.sort(completion);// 정렬
            //System.out.println(Arrays.toString(completion));// 정렬 후: [eden, kiki]


            ArrayList<String> list_participant = new ArrayList<String>(Arrays.asList(participant)); // array -> arrayList 형 변환
            //System.out.println(list_participant);//[eden, kiki, leo]
            ArrayList<String> list_completion = new ArrayList<String>(Arrays.asList(completion)); // array -> arrayList 형 변환
            //System.out.println(list_completion);//[eden, kiki]

            // contains 사용하려면 arrayList 형 변환 필수
            for(int i=0; i<list_participant.size(); i++){
                boolean a = list_completion.contains(list_participant.get(i));// 대상 - 단어
                if(!a) {
                    answer = list_participant.get(i);
                    break;
                }
            }

            if(answer==""){//동명이인
                for(int i=0; i<completion.length; i++){
                    String temp1 = participant[i];
                    String temp2 = completion[i];
                    if(temp1!=temp2){
                        answer = participant[i];
                    }
                }
            }
            //System.out.println(answer);//leo
            return answer;
        }
    }
}

 

다른 사람 배열 -> 성공

import java.util.*;
class Solution {
    public String solution(String[] participant, String[] completion) {
        Arrays.sort(participant);
        Arrays.sort(completion);
        int i;
        for ( i=0; i<completion.length; i++){

            if (!participant[i].equals(completion[i])){
                return participant[i];
            }
        }
        return participant[i];
    }
}

 

 

HashMap -> 성공

import java.util.*;

class Solution {
    public String solution(String[] participant, String[] completion) {
     String answer = "";
        HashMap<String, Integer> hm = new HashMap<>();
        
        for (String player : participant)
            hm.put(player, hm.getOrDefault(player,0)+1);
        
        for (String player : completion)
            hm.put(player, hm.get(player)-1);
        
        for(String key : hm.keySet()){
            if(hm.get(key) !=0){
                answer = key;
                break;
            }
        }
        return answer;
    }
}