PTA[Tree Traversal] Java

Given the post-order traversal and middle-order traversal of a binary tree, please output the sequence of its layer-order traversal. It is assumed that the key values ​​are all positive integers that are not equal to each other.

Input format:

Enter the first line to give a positive integer N (≤30), which is the number of nodes in the binary tree. The second line gives the subsequent traversal sequence. The third line gives the in-order traversal sequence. The numbers are separated by spaces.

Output format:

Output the sequence traversed by the tree in one line. The numbers are separated by 1 space, and there must be no extra spaces at the beginning and end of the line.

Input sample:

7
2 3 1 5 7 6 4
1 2 3 4 5 6 7

Sample output:

4 1 6 3 5 7 2

Code:

import java.io.*;
import java.util.TreeMap;

public class Main {
    
    
	static String[] lrd, ldr;
	static TreeMap<Integer, String> map;

	public static void main(String[] args) throws IOException {
    
    
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
		int n = Integer.parseInt(br.readLine());// 节点个数
		lrd = br.readLine().split(" ");// 后序遍历
		ldr = br.readLine().split(" ");// 中序遍历
		map = new TreeMap<>();
		dlr(0, n - 1, 1, n - 1);
		String s = "";
		for (String value : map.values()) {
    
    
			s += value + " ";
		}
		out.print(s.trim());
		out.flush();
	}

	private static void dlr(int start, int end, int key, int root) {
    
    // 起，止，键，根
		if (start > end)
			return;
		int i = start;
		while (i < end && !lrd[root].equals(ldr[i]))
			i++;
		map.put(key, lrd[root]);// 根
		dlr(start, i - 1, key * 2, root - end + i - 1);// 左
		dlr(i + 1, end, key * 2 + 1, root - 1);// 右
	}
}

operation result