手写代码：通过前序和中序还原二叉树

“`” 参考回答：

//算法1

<pre><code class=""language-c"" lang=""c"">#include <iostream>
#include <fstream>
#include <string>
struct TreeNode
{
struct TreeNode* left;
struct TreeNode* right;
char elem;
};

TreeNode* BinaryTreeFromOrderings(char* inorder, char* preorder, int length)
{
if(length == 0)
{
return NULL;
}
TreeNode* node = new TreeNode;
node->elem = *preorder;
int rootIndex = 0;
for(;rootIndex < length; rootIndex++)
{
if(inorder[rootIndex] == *preorder)
break;
}
node->left = BinaryTreeFromOrderings(inorder, preorder +1, rootIndex);
node->right = BinaryTreeFromOrderings(inorder + rootIndex + 1, preorder + rootIndex + 1, length – (rootIndex + 1));
std::cout<<node->elem<<std::endl;
free(node);
return NULL;
}
int main(int argc, char** argv){
char* pr=""GDAFEMHZ"";
char* in=""ADEFGHMZ""; BinaryTreeFromOrderings(in, pr, 8); printf(""\n""); return 0;}
</code></pre>

<pre><code> "“`