数据结构学习 链式队列的C语言实现

#pragma once
#include <stdio.h>
#include <stdlib.h>
#include <memory.h>

typedef int data_t;
typedef struct linknode
{
  data_t* data;
  struct linknode* next;

}linkqueue, *plinkqueue;

//创建头结点
plinkqueue queue_creat();

//新节点队尾入队
int enqueue(plinkqueue p, data_t val);

//队首出队
data_t dequeue(plinkqueue p);

//打印队列
void queue_show(plinkqueue p);

//释放动态开辟的空间
plinkqueue queue_free(plinkqueue p);

 头文件LinkQueue.h

#include "LinkQueue.h"

plinkqueue queue_creat()
{
  plinkqueue p;
  p = (plinkqueue)malloc(sizeof(linkqueue));
  if(p == NULL)
  {
    return NULL;
  }
  memset(p, 0, sizeof(linkqueue));
  p->data = (data_t*)malloc(sizeof(data_t));
  if(p->data == NULL)
  {
    free(p);
    return NULL;
  }
  *(p->data) = 0;
  p->next = NULL;
  return p;
  
}

int enqueue(plinkqueue p, data_t val)
{
  if(p == NULL)
  {
    printf("Pointer is NULL.\n");
    return -1;
  }
  while(p->next != NULL)
  {
    p = p->next;
  }
  plinkqueue newnode;
  newnode = queue_creat();
  *(newnode->data) = val;
  p->next = newnode;
  return 0;
}

data_t dequeue(plinkqueue p)
{
  if(p == NULL)
  {
    printf("Pointer is NULL.\n");
    return -1;
  }
  data_t temp = 0;
  temp = *(p->next->data);
  p->next = p->next->next;
  return temp;
}

void queue_show(plinkqueue p)
{
  printf("address\tvalue\tnext\n");
  while(p->next != NULL)
  {
    printf("%p\t%d\t%p\n", p->next, *(p->next->data), p->next->next);
    p = p->next;
  }
}


plinkqueue queue_free(plinkqueue p)
{
  if(p == NULL)
  {
    printf("Pointer is NULL.\n");
    return NULL;
  }
  free(p->data);
  free(p);
  return NULL;
}

 函数实现LinkQueue.c

#include "LinkQueue.h"

int main()
{
  plinkqueue p;
  p = queue_creat();

  enqueue(p, 21);
  enqueue(p, 22);
  queue_show(p);
  printf("############\n");
  
  enqueue(p, 24);
  queue_show(p);
  printf("############\n");
  
  data_t ret = 0;
  ret = dequeue(p);
  
  queue_show(p);
  printf("############\n");
  
  printf("value:> %d\n", ret);

  p = queue_free(p);
  return 0;
}

测试函数test.c

运行结果： 

 

 头结点总是指向队首元素，执行三次入队操作后，队首元素值为21，队尾元素值为24。执行一次出队操作后，原先的队首元素21出队，头结点指向新的队首22，得到出队元素的值value为21。