题解 | #合并表记录#

import java.util.Scanner;
import java.util.TreeMap;

// 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.hasNext()) { // 注意 while 处理多个 case
            int n = in.nextInt();
            TreeMap tm = new TreeMap<>();
            for (int i = 1; i <= n; i++) {
                int index = in.nextInt();
                int val = in.nextInt();
                if (tm.containsKey(index)) {
                    Integer valn = (Integer) tm.get(index);
                    tm.replace(index, valn + val);
                } else {
                    tm.put(index, val);
                }
            }

            tm.forEach((m, j)->System.out.println(m + " " + tm.get(m)));
        }
    }
}