题目
![](https://images2018.cnblogs.com/blog/919698/201807/919698-20180703154929017-147528842.png)
解法
import java.util.Map.Entry;
import java.util.Scanner;
import java.util.TreeMap;
public class Main {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
TreeMap<Integer, Integer> map = new TreeMap<>();
int num = sc.nextInt();
for(int i=0;i<num;i++){
int key = sc.nextInt();
int value = sc.nextInt();
if(map.containsKey(key)){
map.replace(key, map.get(key) + value);
}else {
map.put(key, value);
}
}
for(Entry<Integer, Integer> entry: map.entrySet()){
System.out.print(entry.getKey() + " ");
System.out.println(entry.getValue());
}
}
}