[백준] 2751 : 수 정렬하기 2

https://www.acmicpc.net/problem/2751

2751번: 수 정렬하기 2

N의 최대 크기가 1000,000이기 때문에 시간복잡도를 줄이는 게 중요하다고 생각함.

Collections의 sort 메소드를 사용했는데, 그래도 시간이 많이 나온 것 같다.

 

내 코드

메모리 : 129832 KB

시간 : 1416 ms

코드길이 : 670 B

 

[내 코드]

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Collections;

public class Main {

	public static void main(String[] args) throws IOException{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringBuilder sb = new StringBuilder();
		
		int N = Integer.parseInt(br.readLine());
		ArrayList<Integer> arrlist = new ArrayList<>();
		for(int n = 0; n < N; n++) {
			int num = Integer.parseInt(br.readLine());
			arrlist.add(num);
		}
		Collections.sort(arrlist);
		
		for(int i : arrlist) {
			sb.append(i).append('\n');
		}
		System.out.print(sb);
	}

}

 

1등 코드

메모리 : 50312 KB

시간 : 216 ms

코드길이 : 2077 B

 

[상위권 코드]

import java.io.DataInputStream;
import java.io.FileInputStream;
import java.io.IOException;


public class Main {
    static class Reader {
        final private int BUFFER_SIZE = 1 << 16;
        private DataInputStream din;
        private byte[] buffer;
        private int bufferPointer, bytesRead;

        public Reader()
        {
            din = new DataInputStream(System.in);
            buffer = new byte[BUFFER_SIZE];
            bufferPointer = bytesRead = 0;
        }

        public Reader(String file_name) throws IOException
        {
            din = new DataInputStream(
                    new FileInputStream(file_name));
            buffer = new byte[BUFFER_SIZE];
            bufferPointer = bytesRead = 0;
        }

        public String readLine() throws IOException
        {
            byte[] buf = new byte[64]; // line length
            int cnt = 0, c;
            while ((c = read()) != -1) {
                if (c == '\n') {
                    if (cnt != 0) {
                        break;
                    }
                    else {
                        continue;
                    }
                }
                buf[cnt++] = (byte)c;
            }
            return new String(buf, 0, cnt);
        }

        public int nextInt() throws IOException
        {
            int ret = 0;
            byte c = read();
            while (c <= ' ') {
                c = read();
            }
            boolean neg = (c == '-');
            if (neg)
                c = read();
            do {
                ret = ret * 10 + c - '0';
            } while ((c = read()) >= '0' && c <= '9');

            if (neg)
                return -ret;
            return ret;
        }

        public long nextLong() throws IOException
        {
            long ret = 0;
            byte c = read();
            while (c <= ' ')
                c = read();
            boolean neg = (c == '-');
            if (neg)
                c = read();
            do {
                ret = ret * 10 + c - '0';
            } while ((c = read()) >= '0' && c <= '9');
            if (neg)
                return -ret;
            return ret;
        }

        public double nextDouble() throws IOException
        {
            double ret = 0, div = 1;
            byte c = read();
            while (c <= ' ')
                c = read();
            boolean neg = (c == '-');
            if (neg)
                c = read();

            do {
                ret = ret * 10 + c - '0';
            } while ((c = read()) >= '0' && c <= '9');

            if (c == '.') {
                while ((c = read()) >= '0' && c <= '9') {
                    ret += (c - '0') / (div *= 10);
                }
            }

            if (neg)
                return -ret;
            return ret;
        }

        private void fillBuffer() throws IOException
        {
            bytesRead = din.read(buffer, bufferPointer = 0,
                    BUFFER_SIZE);
            if (bytesRead == -1)
                buffer[0] = -1;
        }

        private byte read() throws IOException
        {
            if (bufferPointer == bytesRead)
                fillBuffer();
            return buffer[bufferPointer++];
        }

        public void close() throws IOException
        {
            if (din == null)
                return;
            din.close();
        }
    }
    
      public static void main(String[] args) throws IOException {
        Reader sc = new Reader();
        int N = sc.nextInt();
        int size = 2000001;
        int [] arr = new int[size];

        for (int i = 0; i < N; i++){
            int idx = sc.nextInt();
            arr [idx + 1000000] ++;
        }

        StringBuilder str = new StringBuilder("");

        for (int i=0; i < size; i++){
            if (arr[i] != 0){
                str.append(i - 1000000);
                str.append("\n");
            }
        }

        System.out.println(str.toString());
    }
}