백준 - 가운데를 말해요 (1655)

https://www.acmicpc.net/problem/1655

중간값을 기준으로 작은 값은 maxHeap, 큰값은 minHeap에 저장한다. 중간값은 언제나 minHeap에 저장한다.

import java.util.*;
import java.io.*;

public class Main {
    private static BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
    private static BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(System.out));
    
    private static PriorityQueue<Integer> right = new PriorityQueue<>();
    private static PriorityQueue<Integer> left = new PriorityQueue<>(Comparator.reverseOrder());
    
    public static void main(String[] args) throws IOException {
        int N = Integer.parseInt(reader.readLine());
        StringBuilder result = new StringBuilder();
        
        // i = 0
        left.add(Integer.parseInt(reader.readLine()));
        result.append(left.peek()).append(System.lineSeparator());
        
        if (N < 2) {
            System.out.print(result);
            return;
        }
        
        // i = 1
        Integer t = Integer.parseInt(reader.readLine());
        if (left.peek() <= t) {
            right.add(t);
        } else {
            right.add(left.poll());
            left.add(t);
        }
        
        result.append(left.peek()).append(System.lineSeparator());
        
        for (int i = 2; i < N; i++) {
            Integer number = Integer.parseInt(reader.readLine());
            Integer leftMiddle = left.peek();
            Integer rightMiddle = right.peek();
            
            if (i % 2 == 0) {
                if (number <= rightMiddle) {
                    left.add(number);
                } else {
                    left.add(right.poll());
                    right.add(number);
                }
            } else {
                if (number < leftMiddle) {
                    right.add(left.poll());
                    left.add(number);
                } else {
                    right.add(number);
                }
            }
            
            result.append(left.peek()).append(System.lineSeparator());
        }
        
        System.out.print(result);
    }
}

• StringBuffer에 모든 결과를 다 합친 후에 마지막에 한번에 결과를 출력하면 속도가 빠르다.