根据中序序列与后序序列构建二叉树

BinaryTree* Creat_Node(char ch)
{
    BinaryTree* root;
    root = new BinaryTree;
    root->data = ch;
    root->lchild = root->rchild = NULL;
    return root;
}

BinaryTree* Mid_Post_Create_Pre(char* mid,char*post,int N)
{
    if(!mid||!post||N<0){
            cout<<"输入出错！"<<endl;
        return NULL;                
    }
    int root_index = 0;
    for(root_index = 0 ; root_index < N ; root_index++){
        if(mid[root_index] == post[N-1]){
            break;
        }
    }
    if(root_index == N){
        cout<<"中序序列与后序序列不匹配！"<<endl;
        return NULL;
    }
    BinaryTree* root = this->Creat_Node(post[N-1]);
    if(root_index > 0){
        root->lchild = root->Mid_Post_Create_Pre(mid,post,root_index); 
    }
    if(N-root_index-1 > 0){
        root->rchild = root->Mid_Post_Create_Pre(mid+root_index+1,post+root_index,N-root_index-1);
    }
    return root; 
}