题解 | #合并表记录#

1、使用treemap来保证key的去重加有序，遍历map时，可以用iterator或for-each

import java.util.Iterator;
import java.util.Map;
import java.util.Scanner;
import java.util.TreeMap;


public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int num = in.nextInt();
        //使用treemap来保证去重加排序
        Map<Integer, Integer> map = new TreeMap<>();
        for(int i = 0; i < num; i++){
            int index = in.nextInt();
            int value = in.nextInt();
            if(!map.containsKey(index)){
                map.put(index, value);
            }else{
                int oldvalue = map.get(index);
                int newvalue = oldvalue + value;
                map.put(index, newvalue);
            }
        }
        //使用迭代器来遍历treemap，map.keySet()将map的key变成set
        Iterator<Integer> keyIterator = map.keySet().iterator();
        while(keyIterator.hasNext()){
            int key = keyIterator.next();
            System.out.print(key + " ");
            System.out.print(map.get(key));
            System.out.println();
        }
    }
}