二叉树的构造

struct Node{
    char data;
    Node* right, *left;
};
class Bitree{
public:
    Bitree(){
        root = new Node();
        root->left = nullptr;
        root->right = nullptr;
    }
    void CreateBitree(string &s){
        int pos = -1;
        root = Create(s,pos);
    }
    Node* Create(string &s, int &pos){// 注意这里的pos一定要写成引用，否则不能保证pos的累加
        pos++;
        Node* node ;
        if(pos > s.size()) return nullptr;
        else  if(s[pos] == '#') node = nullptr;
        else{
            node = new Node();
            node->data = s[pos];
            node->left = Create(s, pos);
            node->right = Create(s, pos);
        }
        return node;
    }
    
    void preorder(Node* p){
        if(!p) return;
        cout<< p->data<<endl;
        preorder(p->left);
        preorder(p->right);
    }
    Node* root;
};


int main(){
    string s = "ABD##E#F##C##";
    Bitree t;
    t.CreateBitree(s); //通过先序遍历的顺序构造二叉树
    t.preorder(t.root);
    return 0;

}