由二叉树的前、中序遍历结果求后序遍历结果

可把实际序列换成所需的序列

#include <iostream>  
  #include <fstream>  
 #include <string>  
 
using namespace std;


struct TreeNode
 {
    struct TreeNode* left;
    struct TreeNode* right;
    char  elem;
 };
 
 void BinaryTreeFromOrderings(char* inorder, char* preorder, int length)
 {
   if(length == 0)
     {
       //cout<<"invalid length";
       return;
     }
   TreeNode* node = new TreeNode;//Noice that [new] should be written out.
   node->elem = *preorder;
   int rootIndex = 0;
   for(;rootIndex < length; rootIndex++)
     {
       if(inorder[rootIndex] == *preorder)
       break;
     }
   //Left
   BinaryTreeFromOrderings(inorder, preorder +1, rootIndex);
   //Right
   BinaryTreeFromOrderings(inorder + rootIndex + 1, preorder + rootIndex + 1, length - (rootIndex + 1));
   cout<<node->elem<<endl;
   return;
 }
 
 
 int main(int argc, char* argv[])
 {
     //printf("Hello World!\n");
     char* pr="ACDEFHGB";
     char* in="DECAHFBG";
   
     BinaryTreeFromOrderings(in, pr, 8);


     printf("\n");
     return 0;
 }