题解 | #合并表记录#

import java.util.Scanner;
import java.util.HashMap;
import java.util.ArrayList;
import java.util.Collections;

// 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);
        String count = in.nextLine();
        HashMap<Integer, Integer> map = new HashMap<>();
        for (int i = 0; i < Integer.parseInt(count); i++) {
            String num = in.nextLine();
            String[] nums = num.split(" ");
            Integer key = Integer.valueOf(nums[0]);
            Integer value = Integer.valueOf(nums[1]);
            if (!map.containsKey(key)) {
                map.put(key, value);
            } else {
                map.put(key, map.get(key) + value);
            }
        }
        ArrayList<Integer> list = new ArrayList<>(map.keySet());
        Collections.sort(list);
        for(Integer i:list) {
            System.out.println(i + " " + map.get(i));
        }
    }
}