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);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextInt()) { // 注意 while 处理多个 case
            int times = in.nextInt();
            TreeMap<Integer, Integer> counter = new TreeMap<>();
            while (times-- > 0) {
                int key = in.nextInt();
                int value = in.nextInt();
                counter.compute(key, (k, v) -> {
                   if (v == null) return value;                       
                   else return v + value;
                });
            }
            for (Integer i : counter.keySet()) {
               System.out.println(i + " " + counter.get(i));
            }
            counter.clear();
        }
    }
}