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！