题解 | #合并表记录#
合并表记录
https://www.nowcoder.com/practice/de044e89123f4a7482bd2b214a685201
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.io.StreamTokenizer;
import java.util.*;
public class Main{
public static void main(String[] args) throws Exception{
Scanner sc = new Scanner(System.in);
int size = sc.nextInt();
HashMap<Integer, Integer> map = new HashMap<>();
for(int i = 0; i < size; i++){
int index = sc.nextInt();
int value = sc.nextInt();
map.put(index, map.getOrDefault(index, 0)+value);
}
ArrayList<Map.Entry<Integer, Integer>> list = new ArrayList<>(map.entrySet());
Collections.sort(list, new Comparator<Map.Entry<Integer, Integer>>(){
public int compare(Map.Entry<Integer, Integer> o1, Map.Entry<Integer, Integer> o2){
return o1.getKey()-o2.getKey();
}
} );
for(Map.Entry<Integer, Integer> entry : list){
System.out.println(entry.getKey() + " " + entry.getValue());
}
}
}
关键在于对map的排序，有两个方法
1.使用TreeMap代替HashMap
2.将HashMap中的entrySet取出到List中，再进行排序
