题解 | #合并表记录#

import java.util.HashMap;
import java.util.Map;
import java.util.Scanner;
import java.util.TreeSet;
import java.util.Iterator;

// 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);
        int n = Integer.valueOf(in.nextLine());
        Map<Integer,Integer> map = new HashMap<>();
        TreeSet<Integer> tree = new TreeSet<>();
        for(int i=0;i<n;i++){
            String input = in.nextLine();
            String[] arr = input.split(" ");
            Integer temp = map.get(Integer.valueOf(arr[0]));
            if(temp == null) {
                map.put(Integer.valueOf(arr[0]), Integer.valueOf(arr[1]));
                tree.add(Integer.valueOf(arr[0]));
            } else {
                map.put(Integer.valueOf(arr[0]), temp+Integer.valueOf(arr[1]));
            }
        }
        // 注意 hasNext 和 hasNextLine 的区别
        Iterator<Integer> its = tree.iterator();
        while(its.hasNext()) {
            Integer i = its.next();
            System.out.println(i+" "+map.get(i));
        }
    }
}