题解 | #合并表记录#

import java.util.Scanner;
import java.util.HashMap;

// 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) {
        HashMap<Integer, Integer> num = new HashMap<>();
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        for (int i = 0; i < n; i++) {
            int key = sc.nextInt();
            int value = sc.nextInt();
            num.put(key, num.getOrDefault(key, 0) + value);
        }
        num.keySet().stream().sorted().forEach((Integer integer)->System.out.println(
                integer + " " + num.get(integer)));
    }
}