由二叉树的中序遍历， 前序遍历， 构建二叉树

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;//Noice that [new] should be written out.
　　node->elem = *preorder;
　　int rootIndex = 0;
　　for(;rootIndex < length; rootIndex++)//a variation of the loop
　　{
　　　　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;
　　return node;
　　}

　　int main(int argc, char** argv){
　　char* pr="GDAFEMHZ";
　　char* in="ADEFGHMZ";

　　BinaryTreeFromOrderings(in, pr, 8);

　　 printf("\n");

　　return 0;

}

//或者直接输出后续遍历

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="GDAFEMHZ";
char* in="ADEFGHMZ";

BinaryTreeFromOrderings(in, pr, 8);

printf("\n");
return 0;
}