题解 | #合并表记录#

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

// 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 scanner = new Scanner(System.in);
        Map<Integer, Integer> map = new TreeMap<>();
        int n = scanner.nextInt();
        {
            for (int i = 0; i < n; i++) {
                int key = scanner.nextInt();
                int value = scanner.nextInt();
                if (map.containsKey(key)) {
                    map.replace(key, value + map.get(key));
                } else {
                    map.put(key, value);
                }
            }
        }
        
        for (Map.Entry<Integer, Integer> entry : map.entrySet()) {
            System.out.println(entry.getKey() + " " + entry.getValue());
        }
    }
}