题解 | #合并表记录#

import java.util.*;
public class Main {
    public static void main(String[] args){
        Scanner in = new Scanner(System.in);
        Map<Integer,Integer> map = new TreeMap<>();
        int n = in.nextInt();
        for(int i = 0 ; i < n ;i++){
            int k = in.nextInt();
            int v = in.nextInt();
            map.put(k,map.getOrDefault(k,0)+v);
        }
        for(int i :map.keySet()){
            System.out.println(i+" "+ map.get(i));
        }
    }
}