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K번째수/programmers/level1/java/sort()/copyOfRange() 2020.02.11

K번째수/programmers/level1/java/sort()/copyOfRange()

2020. 2. 11. 09:43

https://programmers.co.kr/learn/courses/30/lessons/42748

코딩테스트 연습 - K번째수 | 프로그래머스

[1, 5, 2, 6, 3, 7, 4] [[2, 5, 3], [4, 4, 1], [1, 7, 3]] [5, 6, 3]

programmers.co.kr

< K번째수 >

○ 시행착오

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class Solution {
    public int[] solution(int[] array, int[][] commands) {
        int[] answer = new int[commands.length];//commands의 i값 만큼 만들기
        int temp=0;
        int count=0;
        
        for(int i=0 ; i<commands.length; i++){
            for(int j=commands[i][0]-1 ; j< commands[i][1]-1;j++){
                 if(array[commands[i][0]-1]>array[commands[i][0]]){
                        temp=array[commands[i][0]];
                        array[commands[i][0]]=array[commands[i][0]-1];
                        array[commands[i][0]-1]=temp;
                            count++;
                    }             
            }if(count==0){
                
                answer[i]=array[commands[i][2]];
                break;
            }
        }
        return answer;
    }
}
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1.인덱스의 값을 제대로 확인하지 않았다. 
2.i와 j가 같은 때를 생각하지 않았다. 
3."자른후 정렬" 자르지않고 그대로 인덱스 값만 해주면 배열의 위치가 바뀌기 때문에 다음번째 정렬 되있을때 처음 배열 상태가 아니므로 무조건 잘라서 해야한다.
 

○ 테스트는 성공하지만 풀이 제출시 실패한 풀이

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class Solution {
    public int[] solution(int[] array, int[][] commands) {
        int[] answer = new int[commands.length];
        int temp=0;
        int count=0;
        int[][] arr1= new int[commands.length][array.length];
        
        //자르면서 배열 복사
        for(int i=0 ;i<commands.length; i++){
            for(int j=commands[i][0]-1, k=0;j<=commands[i][1]-1; j++,k++)
                arr1[i][k]=array[j];
        }
        //버블정렬
        for(int i=0 ; i<commands.length; i++){
            if(commands[i][0]==commands[i][1]){
                answer[i]=arr1[i][commands[i][2]-1];
                continue;
                }
            for(int k=0; k<commands[i][1]-2; k++){
            for(int j=0 ; j<commands[i][1]-2;j++){
                 if(arr1[i][j]>arr1[i][j+1]){
                        temp=arr1[i][j];
                       arr1[i][j]=arr1[i][j+1];
                        arr1[i][j+1]=temp;
                               
                    } 
                }
            }
            answer[i]=arr1[i][commands[i][2]-1];
        }
        return answer;
    }
}
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1.테스트는 성공했는데 코드 제출했을 때 한개 빼고 모두 실패했다. sort 함수 사용해서 다시 해봐야겠다.

---------------------------------------------------- 여기서부터 성공한 풀이 --------------------------------------------------

○ 다른사람 풀이를 보고 푼 풀이( sort() , copyOfRange() 사용)


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import java.util.Arrays;
class Solution {
    public int[] solution(int[] array, int[][] commands) {
        int[] answer = new int [commands.length];        
        
        for(int i =0; i<commands.length; i++){
         int[] temp= Arrays.copyOfRange(array,commands[i][0]-1,commands[i][1]);
            Arrays.sort(temp);
            answer[i]=temp[commands[i][2]-1];
        }
        
        return answer;
    }
}
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- Arrays.sort(배열) : 배열안에 있는 문자열, 영문자 , 숫자 모두 오름차순으로 정렬 해준다. 
- Arrays.copyOfRange(배열이름,시작,끝) : 배열의 시작과 끝을 정해서 배열로 복사해준다.
 

○ sort() 함수만 사용한 풀이

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import java.util.Arrays;
class Solution {
    public int[] solution(int[] array, int[][] commands) {
        int[] answer = new int [commands.length];        
                  
        for(int i =0; i<commands.length; i++){
            int start =commands[i][0]-1;
            int finish= commands[i][1]-1;
            int pick=commands[i][2]-1;
            int temp[]=new int [finish-start+1];//4-1=3+1=4 -> 0 1 2 3
            
            //배열 복사
            for(int j=start,k=0; j<=finish; j++,k++)//j=1 2 3 4 k=0 1 2 3
                temp[k]=array[j];                
            
            //정렬                   
            Arrays.sort(temp);
            answer[i]=temp[pick];
        }
        return answer;
    }
 }
 
 
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○sort()함수 , copyOfRange()함수 없이 푼 풀이



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import java.util.Arrays;
class Solution {
    public int[] solution(int[] array, int[][] commands) {
        int[] answer = new int [commands.length];        
                  
        for(int i =0; i<commands.length; i++){
            int start =commands[i][0]-1;
            int finish= commands[i][1]-1;
            int pick=commands[i][2]-1;
            int temp[]=new int [finish-start+1];//4-1=3+1=4 -> 0 1 2 3
            
            //배열 복사
            for(int j=start,k=0; j<=finish; j++,k++)//j=1 2 3 4 k=0 1 2 3
                temp[k]=array[j];                
            
            //향상된 버블소트 이용하여 정렬
            int count=0;
            for(int j=0; j<temp.length-1;j++){
                for(int k=0;k<temp.length-1; k++){//0 1 2 
                    int swap;
                    if(temp[k]>temp[k+1]){
                        swap=temp[k];
                        temp[k]=temp[k+1];
                        temp[k+1]=swap;
                        count++;
                    }
                }if(count==0)   //swap이 더이상 일어나지 않는다면 break
                    break;
            }
            //정렬이후 answer에 넣기
            answer[i]=temp[pick];
        }
        return answer;
    }
 }
 
 
 
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cs

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K번째수/programmers/level1/java/sort()/copyOfRange()

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