题解 | #合并表记录#--判断hash的key按key升序

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int num = in.nextInt();
        Map<Integer, Integer> map = new HashMap<>();
        for (int i = 0; i < num; i++) {
            Integer key = in.nextInt();
            Integer value = in.nextInt();
            // 判断是否已存在key
            if (map.containsKey(key)) {
                map.put(key, map.get(key) + value);
            } else {
                map.put(key, value);
            }
        }
        // 按key升序输出
        map.keySet().stream().sorted().forEach(key -> {
            System.out.print(key + " ");
            System.out.println(map.get(key));
        });
    }
}