题解 | #合并表记录#

import java.util.*;
public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int num = scanner.nextInt();
        HashMap<Integer, Integer> map = new HashMap<>();
        for (int i = 0; i < num; i++) {
            int k = scanner.nextInt();
            int v = scanner.nextInt();
            map.merge(k, v, Integer::sum);
        }
        map.keySet().stream().sorted().forEach(k -> System.out.println(k + " " + map.get(k)));
    }
}