数据结构基础(3)-->队列

queue.h

#ifndef QUEUE_H
#define QUEUE_H     1
#include <stdio.h>
#include <string.h>
#include <malloc.h>

#define QUEUE_NODE_MAX      1024

struct qnode
{
    char        name[32];
    int     num;
    struct  qnode   *next;
};
struct queue
{
    int     queuesize;
    struct  qnode   *head;
    struct  qnode   *tail;
};

int initqueue(struct queue **head);
void destroyqueue(struct queue **head);
void clearqueue(struct queue *head);
int queueempty(const struct queue *head);
int queuelength(const struct queue *head);
int queueinsert(struct queue *head, struct qnode *new);
struct qnode *queuedelete(struct queue *head);
void printqnode(const struct qnode *node);
int printqhead(const struct queue *head);

#endif /* QUEUE_H */

queue.c

#include <queue.h>

int initqueue(struct queue **head)
{
    *head = (struct queue *)malloc(sizeof(struct queue));
    if(!*head) {
        return -1;
    }
    (*head)->queuesize = 0;
    memset(*head, 0, sizeof(struct queue));
    (*head)->head = (struct qnode *)malloc(sizeof(struct qnode));
    (*head)->tail = (struct qnode *)malloc(sizeof(struct qnode));
    if(!(*head)->head || (!(*head)->tail)) {
        free((*head)->head);
        free((*head)->tail);
        free(*head);
        *head = NULL;
        return -1;
    }
    strcpy((*head)->head->name, "head");
    (*head)->head->num = 0;
    (*head)->head->next = (*head)->tail;
    strcpy((*head)->tail->name, "tail");
    (*head)->tail->num = 0;
    (*head)->tail->next = (*head)->head;
    return 0;
}
void destroyqueue(struct queue **head)
{
    clearqueue(*head);
    free(*head);
    *head = NULL;
}
void clearqueue(struct queue *head)
{
    struct  qnode   *node;
    while(head->head->next != head->tail) {
        node = head->head->next->next;
        free(head->head->next);
        head->head->next = node;
    }
}
int queueempty(const struct queue *head)
{
    return head->head->next == head->tail;
}
int queuelength(const struct queue *head)
{
    return head->queuesize;
}
int queueinsert(struct queue *head, struct qnode *new)
{
    if(QUEUE_NODE_MAX == head->queuesize) {
        return -1;
    }
    ++(head->queuesize);
    new->next = head->tail;
    head->tail->next->next = new;
    head->tail->next = new;
    return 0;
}
struct qnode *queuedelete(struct queue *head)
{
    if(queueempty(head)) {
        return NULL;
    }
    --(head->queuesize);
    struct qnode *node;
    node = head->head->next;
    head->head->next = node->next;
    node->next = NULL;
    if(queueempty(head)) {
        head->tail->next = head->head;
    }
    return node;
}
void printqnode(const struct qnode *node)
{
    if(node) {
        printf("name=%10s, num=%3d...\n", node->name, node->num);
    } else {
        printf("is null...\n");
    }
}
int printqhead(const struct queue *head)
{
    struct qnode *n = head->head;
    do {
        printqnode(n);
        n = n->next;
    }while(n!=head->tail);
    printqnode(n);
    printf("printqhead end...\n");
    return 0;
}