基本数据结构之Binary Search Tree

一、二叉查找树的实现（C）

1）二叉查找树的结点结构

    

typedef struct node
{
    int data;
    struct node* lchild;
    struct node* rchild;
} BSTnode;

2）创建一个新结点

BSTnode* create_node(int data)
{
    BSTnode *new_node = (BSTnode*)malloc(sizeof(BSTnode));
    if(new_node == NULL)
    {
        fprintf (stderr, "Allocate memory error! (create_node)\n");
        exit(1);
    }
    new_node->data = data;
    new_node->lchild = NULL;
    new_node->rchild = NULL;
    return new_node;
}

typedefint(*comparer)(int,int);//compare the node value

3）插入一个

BSTnode* insert_node(BSTnode *root, comparer compare, int data)
{
 
    if(root == NULL)
    {
        root = create_node(data);
    }
    else
    {
        int is_left  = 0;
        int r        = 0;
        BSTnode* cursor = root;
        BSTnode* prev   = NULL;
 
        while(cursor != NULL)
        {
            r = compare(data,cursor->data);
            prev = cursor;
            if(r < 0)
            {
                is_left = 1;
                cursor = cursor->lchild;
            }
            else if(r > 0)
            {
                is_left = 0;
                cursor = cursor->rchild;
            }
 
        }
        if(is_left)
            prev->lchild = create_node(data);
        else
            prev->rchild = create_node(data);
 
    }
    return root;
}

4）删除一个结点

     删除一个结点分三种情况：

      1、该结点没有孩子结点

      2、该结点有一个孩子结点

      3、该结点有两个孩子结点

BSTnode* delete_node(BSTnode* root, int data,comparer compare)
{
    BSTnode *cursor;
    int r = compare(data,root->data);
    BSTnode *parent = NULL;    if(root == NULL)
        return NULL;
 
    
    if( r < 0)
        root->lchild = delete_node( root->lchild, data,compare);
    else if( r > 0 )
        root->rchild = delete_node(root->rchild,data,compare);
    else
    {
        if (root->lchild == NULL)
        {
            cursor = root->rchild;
            free(root);
            root = cursor;
        }
        else if (root->rchild == NULL)
        {
            cursor = root->lchild;
            free(root);
            root = cursor;
        }
        else    //2 children
        {
            cursor = root->rchild;
            
 
            while(cursor->lchild != NULL)
            {
                parent = cursor;
                cursor = cursor->child;
            }
            root->data = cursor->data;
            if (parent != NULL)
                parent->lchild = delete_node(parent->lchild, parent->lchild->data,compare);
            else
                root->rchild = delete_node(root->rchild, root->rchild->data,compare);
        }
    }
    return root;
}

5）查找一个结点

BSTnode* search(BSTnode *root,const int data,comparer compare)
{
    int r;
    BSTnode* cursor = root;
if(root == NULL)
        return NULL;
 
    while(cursor != NULL)
    {
        r = compare(data,cursor->data);
        if(r < 0)
            cursor = cursor->lchild;
        else if(r > 0)
            cursor = cursor->rchild;
        else
            return cursor;
    }
    return cursor;
}

6）遍历这课BST

typedefvoid(*callback)(BSTnode*);

void traverse(BSTnode *root,callback cb)
{
    BSTnode *cursor, *pre;
 
    if(root == NULL)
        return;
 
    cursor = root;
 
    while(cursor != NULL)
    {
        if(cursor->lchild != NULL)
        {
            cb(cursor);
            cursor = cursor->rchild;
        }
        else
        {
            pre = cursor->lchild;
 
            while(pre->rchild != NULL && pre->rchild != cursor)
                pre = pre->rchild;
 
            if (pre->rchild != NULL)
            {
                pre->rchild = cursor;
                cursor = cursor->lchild;
            }
            else
            {
                pre->rchild = NULL;
                cb(cursor);
                cursor = cursor->rchild;
            }
        }
    }
}

7）删除该给定的BST

void dispose(BSTnode* root)
{
    if(root != NULL)
    {
        dispose(root->lchild);
        dispose(root->rchild);
        free(root);
    }
}

8）显示单个结点的值

void display(BSTnode* nd)
{
    if(nd != NULL)
        printf("%d ",nd->data);
}

9）显示整棵树的值

void display_tree(BSTnode* nd)
{
    if (nd == NULL)
        return;
    /* display node data */
    printf("%d",nd->data);
    if(nd->lchild != NULL)
        printf("(L:%d)",nd->lchild->data);
    if(nd->rchild != NULL)
        printf("(R:%d)",nd->rchild->data);
    printf("\n");
 
    display_tree(nd->lchild);
    display_tree(nd->rchild);
}

/*
    compare two integers
*/
int compare(int left,int right)
{
    if(left > right)
        return 1;
    if(left < right)
        return -1;
    return 0;
}

以上便是BST树的C语言实现。

不明白的可以留言！