题解 | #合并表记录#

    public static void main(String[] args) throws IOException{
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.parseInt(reader.readLine());
        Map<Integer, Integer> map = new TreeMap<>();
        for(int i = 0; i < n; i++){
            String str = reader.readLine();
            String[] split = str.split(" ");
            int index = Integer.parseInt(split[0]);
            int num = Integer.parseInt(split[1]);
            map.put(index, map.getOrDefault(index, 0) + num);
        }
        Set<Map.Entry<Integer, Integer>> entries = map.entrySet();
        for(Map.Entry entry : entries){
            System.out.println(entry.getKey() + " " + entry.getValue());
        }
    }