给一个二叉树的前序和中序序列，求二叉树的层序序列

import java.util.Scanner;class Node {char value;Node left;Node right;int signal;public Node() {}public Node(char value, Node left, Node right, int signal) {super();this.value = value;this.left = left;this.right = right;this.signal = signal;}public int getValue() {return value;}public void setValue(char value) {this.value = value;}public Node getLeft() {return left;}public void setLeft(Node left) {this.left = left;}public Node getRight() {return right;}public void setRight(Node right) {this.right = right;}}public class Main {static int k = 0;private static void layerOrder(Node root) {if(root == null) return ;Node[] q = new Node[k];char[] r = new char[k];int start = 0, end = 1;q[start] = root;while(start < end && start < k) {r[start] = q[start].value;if(q[start].left != null) q[end++] = q[start].left;if(q[start].right != null) q[end++] = q[start].right;start++;}System.out.println(new String(r));}private static Node findLayers(char[] prc, char[] inc, int low, int high) {if(low > high) return null;Node root = new Node();char tmp_root = prc[k++];root.setValue(tmp_root);int position_root_in_In = -1;for( int i = low; i <= high; i++ ) {if(tmp_root == inc[i]) {position_root_in_In = i;break;}}Node l = findLayers(prc,inc,low,position_root_in_In-1);Node r = findLayers(prc,inc,position_root_in_In+1,high);root.setLeft(l);root.setRight(r);return root;}public static void main(String[] args) {Scanner sc = new Scanner(System.in);while(sc.hasNext()) {k = 0;String pr = sc.nextLine();String post = sc.nextLine();int len = pr.length();char[] prc = pr.toCharArray();char[] inc = post.toCharArray();char[] layer = new char[len];Node root = new Node();root.setValue(prc[0]);root.setLeft(null);root.setRight(null);Node tree = findLayers(prc,inc,0,len-1);layerOrder(tree);}}}