二叉查找树

1. 查找

Status SearchBST(BiTree T, KeyType key, BiTree f, BiTree &p){
  if(!T) { //查找不成功
    p=f;
    return false;
  }
  else if (key == T->data.key) { //查找成功
    p=T;
    return true;
  }
  else if (key < T->data.key) 
    return SearchBST(T->lchild, key, T, p);
  else 
    return SearchBST(T->rchild, key, T, p);
}

2. 插入

Status InsertBST(BiTree *T, ElemType e){  
      if(!T)  
        {	    
            s = new BiTNode;
            s->data = e; s->lchild = s->rchild = NULL;
            T=s;	//被插節点*s为新的根结点
        }
      else if(e.key == T->data.key)
        return false;//关键字等于e.key的数据元素，返回錯誤
      if (e.key < T->data.key)
	InsertBST(T->lchild, e);	//將e插入左子樹
      else 
	InsertBST(T->rchild, e);	//將e插入右子樹
      return true;
 }

3. 删除

Status DeleteBST(BiTree *T, KeyType key){
  //若二叉查找树T中存在关键字等于key的数据元素时，则删除该数据元素，并返回
  //TRUE；否则返回FALSE
  if(!T) 
    return false;	//不存在关键字等于key的数据元素
  else{
    if(key == T->data.key) { 	//  找到关键字等于key的数据元素
      return Delete(T);
    }
    else if(key < T->data.key)
      return DeleteBST(T->lchild, key);
    else
      return DeleteBST(T->rchild, key);
  }
}

Status Delete(BiTree *p){
  //该节点为叶子节点，直接删除
  BiTree *q, *s;
  if (!p->rchild && !p->lchild)
  {
      delete p;
      p = NULL;
  }
  else if(!p->rchild){	//右子树空则只需重接它的左子树
    q=p->lchild;
    p->data = p->lchild->data;
    p->lchild=p->lchild->lchild;
    p->rchild=p->lchild->rchild;

    delete q;
  }
  else if(!p->lchild){	//左子树空只需重接它的右子树
    q=p->rchild;
    p->data = p->rchild->data;
    p->lchild=p->rchild->lchild;
    p->rchild=p->rchild->rchild;

    delete q;  }
  else{	//左右子树均不空
    q=p; 
    s=p->lchild;
    while(s->rchild){ 
      q=s; 
      s=s->rchild;
    }	//转左，然后向右到尽头
    p->data = s->data;	//s指向被删结点的“前驱”
    if(q!=p)	//q为s的parent, 但q有可能为p
      q->rchild = s->lchild;	//重接*q的右子树
    else 
      q->lchild = s->lchild;	//重接*q的左子树
    delete s;
  }
  return true;
}