已知二叉树以二叉链表存储，编写算法完成：对于树种每个元素值为x的结点，删除以它为根的子树，并释放相应的空间

#include <iostream>
#include <queue>
typedef struct treenode{
    char data;
    struct treenode *left;
    struct treenode *right;
}treenode,*ptreenode;

ptreenode buytreenode(char x)
{
    ptreenode n=(ptreenode) malloc(sizeof (treenode));
    n->data=x;
    n->left= nullptr,n->right= nullptr;
    return n;
}
ptreenode build_tree()
{
    ptreenode root= buytreenode('A');
    root->left= buytreenode('B');
    root->right= buytreenode('C');
    root->left->left= buytreenode('D');
    root->left->right= buytreenode('E');
    root->right->left= buytreenode('F');
    root->right->right= buytreenode('G');
    root->left->left->left= buytreenode('H');
    root->left->left->right= buytreenode('I');
    return root;
}

void free_tree(ptreenode root)//后序释放节点
{
    if(root== nullptr) return;
    free_tree(root->left);
    free_tree(root->right);
    free(root);
}

ptreenode free_x(ptreenode root,char x)
{
    if(root== nullptr) return nullptr;
    if(root->data==x) {
        free_tree(root);
        return nullptr;
    }
    root->left=free_x(root->left,x);
    root->right=free_x(root->right,x);

}

void print_tree(ptreenode root)
{
    std::queue<ptreenode > tmp;
    tmp.push(root);
    int s=tmp.size();
    while(!tmp.empty())
    {
        ptreenode t=tmp.front();
        tmp.pop();
        s--;
        printf("%3c",t->data);
        if(t->left) tmp.push(t->left);
        if(t->right) tmp.push(t->right);
        if (s==0) puts(""),s=tmp.size();
    }
}
int main() {
    ptreenode root=build_tree();
    print_tree(root);
    ptreenode tmp= free_x(root,'B');
    puts("");
    print_tree(tmp);
    
    return 0;
}