Implementation of binary sorting tree (partial)

Implementation of binary sorting tree (partial)

1. Write the pseudo code of SearchBST (T, key) and InsertBST (T, key)

1. SearchBST pseudocode :

   void SearchBST(T,key){
   	if(T为空||T==key) return T;
   	if(T>key)
   		SearchBST(T->lchild,key);
   	else 
   		SearchBST(T->rchild,key);
   }
   

2. InsertBST pseudocode :

   void InsertBST(T,key){
   	if(T为空）{
   		T=new Node；
   		T=key；
   		T->lchild=NULL；
   		T->rchild=NULL；
   		return 1；
   	}else if(T==key) return 0;
   	else if(T>key) 
   		InsertBST(T->lchild,key);
   	else
   		InsertBST(T->rchild,key);
   }
   

2. Write the pseudo code of CreateBST (T) to create a BST tree from the console input. Finally use code to achieve. Use "50 30 80 20 40 90 10 25 35 85 23 88" to create a BST and output the BST in sequence

1. CreateBST pseudocode :

   void CreateBST(T){
   	T=new Node;
   	T->lchild=NULL；
   	T->rchild=NULL；
   	//输入key
   	if(T不空) T=key;
   	while(key!=0){
   		//输入key
   		if(T不空){
   			InsertBST(T,key);
   		}
   	}
   }
   

2. Create a BST tree:

   1. Data type definition:

      typedef struct BSTNode {
      	int data;
      	struct BSTNode* lchild, * rchild;
      }*BSTree;
      

   2. SearchBST function:

      BSTree SearchBST(BSTree T, int key) {
      	if (T == NULL || T->data == key) return T;
      	if (T->data > key)
      		return SearchBST(T->lchild, key);
      	else
      		return SearchBST(T->rchild, key);
      }
      

   3. InsertBST function:

      void InsertBST(BSTree T, int key) {
      	if (T == NULL){
      		T = new BSTNode;
      		T->data = key;
      		T->lchild = NULL;
      		T->rchild = NULL;
      		return;
      		}
      	else if (T->data == key) return;
      	else if (T->data > key)
      		return InsertBST(T->lchild, key);
      	else
      		return InsertBST(T->rchild, key);
      }
      

   4. CreateBST function:

      void CreateBST(BSTree T) {
      	T = new BSTNode;
      	T->lchild = NULL;
      	T->rchild = NULL;
      	int key;
      	cin >> key;
      	if (T != NULL) T->data = key;
      	while (key != 0) {
      		cin >> key;
      		if (T != NULL) {
      			InsertBST(T, key);
      		}
      	}
      }
      

   5. In-order traversal:

      void InOrder(BSTree T) {
      	if (T != NULL) {
      		InOrder(T->lchild);
      		cout << T->data<<" ";
      		InOrder(T->rchild);
      	}
      }
      

   6. main function:

      void main()
      {
      	BSTree T;
      	T = new BSTNode;
      	int key;
      	CreateBST(T);
      	cout << "中序遍历结果为:" << endl;
      	InOrder(T);
      	cin >> key;
      	SearchBST(T, key);
      	InsertBST(T, key);
      	InOrder(T);
      }
      

3. Write the pseudo code of DeleteBST (T, key) to delete the key from T.

Matters needing attention and points:

To delete the keyword key, you must first determine the location of the node where the key is located: ①leaf node ②only left or right subtree nodes ③nodes that have left and right subtrees

①Leaf node: delete the key directly after finding it;

②Only the left or right subtree node: point rchild / lchild of T's parent node to rchild / lchild of T, and move the left and right subtree nodes upward;

③ Nodes in both the left and right subtrees: replace the T node with the direct precursor of T or the rightmost node of the right subtree.