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);
        TreeMap<Integer, Integer> map = new TreeMap<>();//TreeMap自带key从小到大排序
        int n = in.nextInt();
        for (int i = 0; i < n; i++) {
            Integer key = in.nextInt();//不能重新new一个Scanner, 检题系统不支持
            Integer val = in.nextInt();
            if (map.containsKey(key)) {
                map.put(key, map.get(key) + val);
            } else {
                map.put(key, val);
            }
        }
        map.forEach((integer, integer2) -> System.out.println(integer + " " +
                    integer2));
    }
}