[PAT] 1004 Counting Leaves （30 分）Java

A family hierarchy is usually presented by a pedigree tree. Your job is to count those family members who have no child.

Input Specification:

Each input file contains one test case. Each case starts with a line containing

ID K ID[1] ID[2] ... ID[K]

where ID is a two-digit number representing a given non-leaf node, K is the number of its children, followed by a sequence of two-digit ID's of its children. For the sake of simplicity, let us fix the root ID to be 01.

The input ends with

Output Specification:

For each test case, you are supposed to count those family members who have no child for every seniority level starting from the root. The numbers must be printed in a line, separated by a space, and there must be no extra space at the end of each line.

The sample case represents a tree with only 2 nodes, where 01 is the root and 02 is its only child. Hence on the root 01 level, there is 0 leaf node; and on the next level, there is 1 leaf node. Then we should output 0 1 in a line.

Sample Input:

2 1
01 1 02

Sample Output:

0 1

 1 import java.util.Scanner;
 2 import java.util.ArrayList;
 3 import java.util.HashMap;
 4 import java.util.Map;
 5 public class Main{
 6   
 7   public static void main(String[] args){
 8     
 9     Scanner sc = new Scanner(System.in);
10     int n = sc.nextInt();
11     int m = sc.nextInt();
12     int i = 0,j,id,k,child;
13     ArrayList<Integer> list;
14     HashMap<Integer,ArrayList<Integer>> map = new HashMap<>();
15     int[] record = new int[n];
16     
17     while(i < m){
18       id = sc.nextInt();
19       k = sc.nextInt();
20       list = new ArrayList<>();
21       for(j = 0;j < k;j++){
22         child = sc.nextInt();
23         list.add(child);
24       }
25       map.put(id, list);
26       i++;
27     }
28     int p = DFS(map, record,1,0,0);
29     for(i = 0; i < p ;i++){
30       System.out.print(record[i] + " ");
31     }
32     System.out.print(record[i]);
33   }
34   
35   private static int DFS(Map<Integer,ArrayList<Integer>> map, int[] record, int node,int level, int height){
36     ArrayList<Integer> list = map.get(node);
37     if(list == null){
38       record[level]++;
39       return height;
40     }
41     for(Integer integer:list){
42       height = Math.max(height,DFS(map,record,integer,level+1,level+1));
43     }
44     return height;
45   }
46 }