已知中序后序创建二叉树

#include<iostream.h>
#include<string.h>
#include<stdlib.h>
#include<assert.h>

template<class Type>
class BinaryTree
{
public:
struct TreeNode
{
Type data;
TreeNode *leftchild, *rightchild;
};
BinaryTree() {}
~BinaryTree(){}
private:
TreeNode *root;

static TreeNode *_BuyNode()
{
TreeNode *p = (TreeNode *)malloc(sizeof(TreeNode));
assert(p != NULL);
return p;
}

static int find(Type *is, const Type &x, int n)
{
for(int i = 0; i < n; ++i)
{
if(is[i] == x)
return i;
}
return -1;
}

static TreeNode *CreatInPost(Type *post, Type *is, int n)
{
if(post == NULL || is == NULL || n ==0)
return NULL;
else
{
TreeNode *s = _BuyNode();
s->data = post[n-1];

int num = find(is, post[n-1], n);
if(num == -1)
exit(1);
s->leftchild = CreatInPost(post, is,num);//此处放进去的是线序遍历的前num个
s->rightchild = CreatInPost(post+num, is+num +1, n-num-1);//此处减1是因为这是从后序遍历中找的每次最后一个数就被使用了，每次到这里就要将它除掉
return s;
}

}

static void PreOrder(TreeNode *root)
{
if(root != NULL)
{
cout << root->data << " ";
PreOrder(root->leftchild);
PreOrder(root->rightchild);
}
}
public:
void Creat(Type *post, Type *is, int n)
{
if(post != NULL && is != NULL)
root = CreatInPost(post, is, n);
}
void PreOrder()
{
PreOrder(root);
cout << endl;
}
};

int main(void)
{
BinaryTree<int> tree;
int post[] = {34,56,67,45,23,89,78,12};
int is[] = {34,23,56,45,67,12,78,89};
int n = sizeof(post) / sizeof(post[0]);

tree.Creat(post, is, n);
tree.PreOrder();

return 0;
}