[코테3_1] 두 배열 합치기

✔ 내 답 -> 정답

https://hianna.tistory.com/601
JAVA 배열 합치는 방법

import java.util.*;
import java.lang.*;

public class P3_1 {
  public static int[] solution(int[] arr1, int[] arr2) {
            int[] arr = new int[arr1.length+arr2.length];
            System.arraycopy(arr1,0,arr,0,arr1.length);
            System.arraycopy(arr2,0,arr,arr1.length,arr2.length);
            Arrays.sort(arr); 
      
            return arr;
  }
  public static void main(String[] args){
      Scanner kb = new Scanner(System.in);
      int a1 = kb.nextInt();
      int[] arr1= new int[a1];
      for(int i=0;i<a1;i++) arr1[i] = kb.nextInt();
      int a2= kb.nextInt();
      int[] arr2= new int[a2];
      for(int j=0;j<a2;j++) arr2[j] = kb.nextInt();
      for( int x: solution(arr1,arr2)) System.out.print(x+" ");
  }

}

위는 매우 비효율적이다.
강의 처럼 O(n)방법을 사용한다.

✔️ 강의 답

import java.util.*;

public class Main{
	public static ArrayList<Integer> solution(int[] arr1 , int[] arr2){
		ArrayList<Integer> answer = new ArrayList<>();
		int op =0, tp=0;
		
		while(op<arr1.length && tp<arr2.length) {
			if(arr1[op]<=arr2[tp]) {
				answer.add(arr1[op]);
				op++;
			}
			else {
				answer.add(arr2[tp]);
				tp++;
			}
		}
		while(op<arr1.length) answer.add(arr1[op++]);
		while(tp<arr2.length) answer.add(arr2[tp++]);	
		return answer;
			
	}
	
	public static void main(String[] args) {
		Scanner kb = new Scanner(System.in);
		int a1_len = kb.nextInt();
		int[] arr1 = new int[a1_len];
		for(int i=0; i<a1_len;i++) {
			arr1[i]=kb.nextInt();
		}
		int a2_len = kb.nextInt();
		int[] arr2 = new int[a2_len];
		for(int i=0; i<a2_len;i++) {
			arr2[i]=kb.nextInt();
		}
		for(int x : solution(arr1,arr2)) System.out.print(x+" ");
		
	}
	
	
	
}