hihoCoder 1049 后序遍历 最详细的解题报告

 1 import java.util.Scanner;
 2 
 3 public class Main {
 4 
 5     public static String post_order(String preOrder,String inOrder){
 6         if(preOrder.length()>0&&preOrder.length()==inOrder.length()){
 7             char root=preOrder.charAt(0); //获取根节点
 8             int index=inOrder.indexOf(root); //在中序序列中找出根节点的下标
 9             if(index!=-1){
10                 String left=inOrder.substring(0, index);//中序序列中左孩子串
11                 String right=inOrder.substring(index+1);//中序序列中右孩子串
12                 //递归计算并返回计算后的左孩子+右孩子+根节点
13                 return post_order(preOrder.substring(1, left.length()+1),left)
                          +post_order(preOrder.substring(left.length()+1),right)
                          +root;
14             }
15         }
16         return "";
17     }
18     
19     public static void main(String[] args) {
20         Scanner scanner=new Scanner(System.in);
21         System.out.println(post_order(scanner.next(),scanner.next()));
22     }
23 }