[JAVA] 알고리즘 문제풀이 입문 6-5, 6-6

강의: https://inf.run/w779

자바(Java) 알고리즘 문제풀이 입문: 코딩테스트 대비 - 인프런 | 강의

 

6-5번

for문 사용

import java.util.Scanner;

public class Main {
  public String solution(int n, int[] arr){
    String answer = "U";
   
    for(int i = 0; i < n; i++){
      int pos = i+1;
      for(int j = pos; j < n; j++){
        if(i!=j){
          if(arr[i] == arr[j]) return "D";
        }
      }
    }
    return answer;
  }

  public static void main(String[] args){
    Main t = new Main();
    Scanner in = new Scanner(System.in);

    int n = in.nextInt();
    int[] arr = new int[n];
    for(int i = 0; i < n; i++){
      arr[i] = in.nextInt();
    }
    in.close();

    System.out.print(t.solution(n, arr));
  }
}

 

Hashmap 사용

import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.Scanner;

public class Main {
  public String solution(int n, int[] arr){
    String answer = "U";
    HashMap<Integer, Integer> map = new LinkedHashMap<>();
    
    for(int i = 0; i < n; i++){
      if(!map.containsKey(arr[i])){
        map.put(arr[i], i);
      }else return "D";
    }
    return answer;
  }

  public static void main(String[] args){
    Main t = new Main();
    Scanner in = new Scanner(System.in);

    int n = in.nextInt();
    int[] arr = new int[n];
    for(int i = 0; i < n; i++){
      arr[i] = in.nextInt();
    }
    in.close();

    System.out.print(t.solution(n, arr));
  }
}

배열 정렬(Arrays.sort(arr)) 사용

import java.util.Arrays;
import java.util.Scanner;

public class Main {
  public String solution(int n, int[] arr){
    String answer = "U";
    Arrays.sort(arr);

    for(int i = 0; i < n-1; i++){
      if(arr[i] == arr[i+1]) return "D";
    }
    return answer;
  }

  public static void main(String[] args){
    Main t = new Main();
    Scanner in = new Scanner(System.in);

    int n = in.nextInt();
    int[] arr = new int[n];
    for(int i = 0; i < n; i++){
      arr[i] = in.nextInt();
    }
    in.close();

    System.out.print(t.solution(n, arr));
  }
}

 

 

6-6번

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

public class Main {
  public ArrayList<Integer> solution(int n, int[] arr){
    ArrayList<Integer> answer = new ArrayList<>();
    int[] tmp = arr.clone();
    Arrays.sort(tmp);

    for(int i = 0; i < n; i++){
      if(arr[i] != tmp[i]) answer.add(i+1);
    }
    return answer;
  }

  public static void main(String[] args){
    Main t = new Main();
    Scanner in = new Scanner(System.in);

    int n = in.nextInt();
    int[] arr = new int[n];
    for(int i = 0; i < n; i++){
      arr[i] = in.nextInt();
    }
    in.close();

    for(int x : t.solution(n, arr)) System.out.print(x+" ");
  }
}