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 in = new Scanner(System.in);
        Map<Integer, Integer> map = new TreeMap<>();
        int count = in.nextInt();
        in.nextLine();

        while (--count >= 0) {
            int a = in.nextInt();
            int b = in.nextInt();
            map.compute(a, (k, v) -> v == null ? b : v + b);
        }
        map.forEach((k, v) -> System.out.println(k + " " + v));
    }
}