题解 | #合并表记录#

import java.util.*;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
                Scanner scanner = new Scanner(System.in);
        int tableSize = scanner.nextInt();
        Map<Integer, Integer> table = new TreeMap<>();
        for (int i = 0; i < tableSize; i++) {
            int key = scanner.nextInt();
            int value = scanner.nextInt();
/*            if (table.containsKey(key)) {
                table.put(key, table.get(key) + value);
            } else {
                table.put(key, value);
            }*/
            table.put(key, table.getOrDefault(key, 0) + value);
        }
        for (Integer key : table.keySet()) {
            System.out.println( key + " " + table.get(key));
        }
    }
}