C语言二叉树实例

/* tree.h -- binary search tree                          */
/*           no duplicate items are allowed in this tree */
#ifndef _TREE_H_
#define _TREE_H_
#include <stdbool.h>

/* redefine Item as appropriate */
#define SLEN 20
typedef struct item
{
    char petname[SLEN];
    char petkind[SLEN];
} Item;

#define MAXITEMS 10

typedef struct trnode
{
    Item item;
    struct trnode * left;  /* pointer to right branch  */
    struct trnode * right; /* pointer to left branch   */
} Trnode;

typedef struct tree
{
    Trnode * root;         /* pointer to root of tree  */
    int size;              /* number of items in tree  */
} Tree;

/* function prototypes */

/* operation:      initialize a tree to empty          */
/* preconditions:  ptree points to a tree              */
/* postconditions: the tree is initialized to empty    */
void InitializeTree(Tree * ptree);

/* operation:      determine if tree is empty          */
/* preconditions:  ptree points to a tree              */
/* postconditions: function returns true if tree is    */
/*                 empty and returns false otherwise   */
bool TreeIsEmpty(const Tree * ptree);

/* operation:      determine if tree is full           */
/* preconditions:  ptree points to a tree              */
/* postconditions: function returns true if tree is    */
/*                 full and returns false otherwise    */
bool TreeIsFull(const Tree * ptree);

/* operation:      determine number of items in tree   */
/* preconditions:  ptree points to a tree              */
/* postconditions: function returns number of items in */
/*                 tree                                */
int TreeItemCount(const Tree * ptree);

/* operation:      add an item to a tree               */
/* preconditions:  pi is address of item to be added   */
/*                 ptree points to an initialized tree */
/* postconditions: if possible, function adds item to  */
/*                 tree and returns true; otherwise,   */
/*                 the function returns false          */
bool AddItem(const Item * pi, Tree * ptree);

/* operation: find an item in a tree                   */
/* preconditions:  pi points to an item                */
/*                 ptree points to an initialized tree */
/* postconditions: function returns true if item is in */
/*                 tree and returns false otherwise    */
bool InTree(const Item * pi, const Tree * ptree);

/* operation:      delete an item from a tree          */
/* preconditions:  pi is address of item to be deleted */
/*                 ptree points to an initialized tree */
/* postconditions: if possible, function deletes item  */
/*                 from tree and returns true;         */
/*                 otherwise the function returns false*/
bool DeleteItem(const Item * pi, Tree * ptree);

/* operation:      apply a function to each item in    */
/*                 the tree                            */
/* preconditions:  ptree points to a tree              */
/*                 pfun points to a function that takes*/
/*                 an Item argument and has no return  */
/*                 value                               */
/* postcondition:  the function pointed to by pfun is  */
/*                 executed once for each item in tree */
void Traverse (const Tree * ptree, void (* pfun)(Item item));

/* operation:      delete everything from a tree       */
/* preconditions:  ptree points to an initialized tree */
/* postconditions: tree is empty                       */
void DeleteAll(Tree * ptree);

#endif

/* tree.c -- tree support functions */
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include "tree.h"

/* local data type */
typedef struct pair {
    Trnode * parent;
    Trnode * child;
} Pair;

/* protototypes for local functions */
static Trnode * MakeNode(const Item * pi);
static bool ToLeft(const Item * i1, const Item * i2);
static bool ToRight(const Item * i1, const Item * i2);
static void AddNode (Trnode * new_node, Trnode * root);
static void InOrder(const Trnode * root, void (* pfun)(Item item));
static Pair SeekItem(const Item * pi, const Tree * ptree);
static void DeleteNode(Trnode **ptr);
static void DeleteAllNodes(Trnode * ptr);

/* function definitions */
void InitializeTree(Tree * ptree)
{
    ptree->root = NULL;
    ptree->size = 0;
}

bool TreeIsEmpty(const Tree * ptree)
{
    if (ptree->root == NULL)
        return true;
    else
        return false;
}

bool TreeIsFull(const Tree * ptree)
{
    if (ptree->size == MAXITEMS)
        return true;
    else
        return false;
}

int TreeItemCount(const Tree * ptree)
{
    return ptree->size;
}

bool AddItem(const Item * pi, Tree * ptree)
{
    Trnode * new_node;

    if  (TreeIsFull(ptree))
    {
        fprintf(stderr,"Tree is full\n");
        return false;             /* early return           */
    }
    if (SeekItem(pi, ptree).child != NULL)
    {
        fprintf(stderr, "Attempted to add duplicate item\n");
        return false;             /* early return           */
    }
    new_node = MakeNode(pi);      /* points to new node     */
    if (new_node == NULL)
    {
        fprintf(stderr, "Couldn't create node\n");
        return false;             /* early return           */
    }
    /* succeeded in creating a new node */
    ptree->size++;

    if (ptree->root == NULL)      /* case 1: tree is empty  */
        ptree->root = new_node;   /* new node is tree root  */
    else                          /* case 2: not empty      */
        AddNode(new_node,ptree->root); /* add node to tree  */

    return true;                  /* successful return      */
}

bool InTree(const Item * pi, const Tree * ptree)
{
    return (SeekItem(pi, ptree).child == NULL) ? false : true;
}

bool DeleteItem(const Item * pi, Tree * ptree)
{
    Pair look;

    look = SeekItem(pi, ptree);
    if (look.child == NULL)
        return false;

    if (look.parent == NULL)      /* delete root item       */
        DeleteNode(&ptree->root);
    else if (look.parent->left == look.child)
        DeleteNode(&look.parent->left);
    else
        DeleteNode(&look.parent->right);
    ptree->size--;

    return true;
}

void Traverse (const Tree * ptree, void (* pfun)(Item item))
{

    if (ptree != NULL)
        InOrder(ptree->root, pfun);
}

void DeleteAll(Tree * ptree)
{
    if (ptree != NULL)
        DeleteAllNodes(ptree->root);
    ptree->root = NULL;
    ptree->size = 0;
}


/* local functions */
static void InOrder(const Trnode * root, void (* pfun)(Item item))
{
    if (root != NULL)
    {
        InOrder(root->left, pfun);
        (*pfun)(root->item);
        InOrder(root->right, pfun);
    }
}

static void DeleteAllNodes(Trnode * root)
{
    Trnode * pright;

    if (root != NULL)
    {
        pright = root->right;
        DeleteAllNodes(root->left);
        free(root);
        DeleteAllNodes(pright);
    }
}

static void AddNode (Trnode * new_node, Trnode * root)
{
    if (ToLeft(&new_node->item, &root->item))
    {
        if (root->left == NULL)      /* empty subtree       */
            root->left = new_node;   /* so add node here    */
        else
            AddNode(new_node, root->left);/* else process subtree*/
    }
    else if (ToRight(&new_node->item, &root->item))
    {
        if (root->right == NULL)
            root->right = new_node;
        else
            AddNode(new_node, root->right);
    }
    else                         /* should be no duplicates */
    {
        fprintf(stderr,"location error in AddNode()\n");
        exit(1);
    }
}

static bool ToLeft(const Item * i1, const Item * i2)
{
    int comp1;

    if ((comp1 = strcmp(i1->petname, i2->petname)) < 0)
        return true;
    else if (comp1 == 0 &&
             strcmp(i1->petkind, i2->petkind) < 0 )
        return true;
    else
        return false;
}

static bool ToRight(const Item * i1, const Item * i2)
{
    int comp1;

    if ((comp1 = strcmp(i1->petname, i2->petname)) > 0)
        return true;
    else if (comp1 == 0 &&
             strcmp(i1->petkind, i2->petkind) > 0 )
        return true;
    else
        return false;
}

static Trnode * MakeNode(const Item * pi)
{
    Trnode * new_node;

    new_node = (Trnode *) malloc(sizeof(Trnode));
    if (new_node != NULL)
    {
        new_node->item = *pi;
        new_node->left = NULL;
        new_node->right = NULL;
    }

    return new_node;
}

static Pair SeekItem(const Item * pi, const Tree * ptree)
{
    Pair look;
    look.parent = NULL;
    look.child = ptree->root;

    if (look.child == NULL)
        return look;                        /* early return   */

    while (look.child != NULL)
    {
        if (ToLeft(pi, &(look.child->item)))
        {
            look.parent = look.child;
            look.child = look.child->left;
        }
        else if (ToRight(pi, &(look.child->item)))
        {
            look.parent = look.child;
            look.child = look.child->right;
        }
        else       /* must be same if not to left or right    */
            break; /* look.child is address of node with item */
    }

    return look;                       /* successful return   */
}

static void DeleteNode(Trnode **ptr)
/* ptr is address of parent member pointing to target node  */
{
    Trnode * temp;

    if ( (*ptr)->left == NULL)
    {
        temp = *ptr;
        *ptr = (*ptr)->right;
        free(temp);
    }
    else if ( (*ptr)->right == NULL)
    {
        temp = *ptr;
        *ptr = (*ptr)->left;
        free(temp);
    }
    else    /* deleted node has two children */
    {
        /* find where to reattach right subtree */
        for (temp = (*ptr)->left; temp->right != NULL;
             temp = temp->right)
            continue;
        temp->right = (*ptr)->right;
        temp = *ptr;
        *ptr =(*ptr)->left;
        free(temp);
    }
}