题解 | #合并表记录#

import java.util.*;
public class Main {
    public static void main(String[] args) {
        TreeMap<Object, Object> treeMap = new TreeMap<>(new Comparator<Object>() {
            @Override
            public int compare(Object o1, Object o2) {
                return (int)o1 - (int)o2;
            }
        });
        Scanner scanner = new Scanner(System.in);
        int index;
        int value;
        int num = scanner.nextInt();
        for (int i = 0; i < num; i++) {
            index = scanner.nextInt();
            value = scanner.nextInt();
            if (!treeMap.containsKey(index)) {
                treeMap.put(index, value);
            } else {
                Object o = treeMap.get(index);
                treeMap.put(index, value + (int)o);
            }
            
        }

        Set<Object> keySet = treeMap.keySet();
        for (Object keys : keySet) {
            int key = (int) keys;
            System.out.println(key + " " + treeMap.get(key));
        }
    }
}