后面補(bǔ)充

import java.util.*;

public class Test16 {

private static class TreeNode {
         int val;
         TreeNode left;
         TreeNode right;
         TreeNode(int x) { val = x; left=null;right=null;}
    }
    
    public static void main(String[] args) {

        Scanner scanner  = new Scanner(System.in);

        while(scanner.hasNext()){

            int count = scanner.nextInt();
            
            int[] preArr = new int[count];
            int[] inArr = new int[count];
            
            for (int i = 0; i < count; i++) {
                preArr[i] = scanner.nextInt();
            }
            for (int i = 0; i < count; i++) {
                inArr[i] = scanner.nextInt();
            }
            
            TreeNode node =  name(preArr, inArr, 0, preArr.length-1, 0, inArr.length-1);
            
            ArrayList<Integer> list = new ArrayList<>();
            print(node,list);
            for (int i = 0; i < list.size(); i++) {
                System.out.print(list.get(i));
                if (list.size()-1!=i) {
                    System.out.print(" ");
                }
            }
            
        }

    }
    
    public static TreeNode name(int[] preArr,int[] inArr,int startPre,int endPre,int startIn,int endIn) {
    
        if ( startIn > endIn) {
            return null;
        }
        
        TreeNode tree = new TreeNode(preArr[startPre]);
        
        for ( int i = startIn ; i <= endIn ; i++ ) {
            
            if ( preArr[startPre] ==  inArr[i]) {
                
                tree.left = name(preArr, inArr, startPre+1, i-startIn+startPre, startIn, i-1);
                
                tree.right = name(preArr, inArr, i-startIn+startPre+1, endPre, i+1, endIn);
                
                break;
            }

        }
        
        return tree;
        
    }
    
    private static void print(TreeNode node,ArrayList<Integer> list) {  
        if (node == null)  
            return;  
        print(node.left,list);  
        print(node.right,list);  
//        System.out.print(node.val + " "); 
        list.add(node.val);
    }  


}