c語言實現隊列的先進先出操作

隊列的特點是先進先出，有一個隊列頭和一個隊列尾。如下圖示：整個隊列含有一個隊列頭指針front和一個隊列尾指針rear，並且隊列中每個節點中包含一個數據域和一個指向下一個節點的指針域。

定義一個節點：

typedef struct _node{
	int data;
	struct _node *next;
}node;

定義隊列結構體：

typedef struct {
	node *front;
	node *rear;
}queue;

---

1.創建一個隊列

queue *create_queue(void)
{
	queue * myqueue = (queue *)malloc(sizeof(queue));
	myqueue->front = NULL;
	myqueue->rear = NULL;

	return myqueue;
}

2.入隊

申請一個隊列的節點--節點成員賦值--如果空隊列--隊列的頭尾都指向新的節點--不爲空--隊列的尾下一個節點指針指向新隊列--更新隊列的隊尾指針也就是將隊尾指向新的節點。 

queue *insert_queue(queue *myqueue, int data)
{
	if (NULL == myqueue){
		printf("myqueue is NULL\n");
		return NULL;
	}
	node *new_node = NULL;
	new_node = (node *)malloc(sizeof(node));//create a new node
	new_node->data = data;
	new_node->next = NULL;

	if (myqueue->rear == NULL){//if the queue is empty
		myqueue->front = myqueue->rear = new_node;
	}
	else{
		myqueue->rear->next = new_node;
		myqueue->rear = new_node;//move queue rear pointer to new_node
	}

	return myqueue;
}

 

3.出隊

申請一個節點指針並指向隊列頭--移動隊列頭指針到隊列放入下一個節點--判斷隊列頭是否爲空--釋放需要刪除的節點。 

queue *delete_queue(queue *myqueue)
{
	node *p_node = NULL;
	p_node = myqueue->front;
	if (NULL == p_node){
		printf("this is empty queue\n");
		return NULL;
	}
	else{
		myqueue->front = myqueue->front->next;
		if (myqueue->front == NULL){
			myqueue->rear = NULL;
		}
		free(p_node);
	}

	return myqueue;
}

 

4.獲得隊列的長度和打印一個隊列

int get_queue_length(queue *myqueue)
{
	node *p_node = NULL;
	int len = 0;

	p_node = myqueue->front;
	if (NULL != p_node){
		len = 1;
	}
	while (p_node != myqueue->rear)
	{
		p_node = p_node->next;
		len++;
	}

	return len;
}

void queue_print(queue *myqueue)
{
	node *p_node = NULL;
	p_node = myqueue->front;

	if (NULL == p_node){
		printf("this is empty queue\n");
		return;
	}
	printf("The queue is :");
	while (p_node != myqueue->rear)
	{
		printf("%2d", p_node->data);
		p_node = p_node->next;
	}
	printf("%2d\n", p_node->data);
}

 

5.完整的測試代碼

// ConsoleApplication1.cpp : 定義控制檯應用程序的入口點。
//

// test.cpp : 定義控制檯應用程序的入口點。
//

#include "stdafx.h"
#include <iostream>
#pragma warning(disable:4996)
#include <string>

using namespace std;

typedef struct _node{
	int data;
	struct _node *next;
}node;

typedef struct {
	node *front;
	node *rear;
}queue;

queue *create_queue(void)
{
	queue * myqueue = (queue *)malloc(sizeof(queue));
	myqueue->front = NULL;
	myqueue->rear = NULL;

	return myqueue;
}

//insert queue
queue *insert_queue(queue *myqueue, int data)
{
	if (NULL == myqueue){
		printf("myqueue is NULL\n");
		return NULL;
	}
	node *new_node = NULL;
	new_node = (node *)malloc(sizeof(node));//create a new node
	new_node->data = data;
	new_node->next = NULL;

	if (myqueue->rear == NULL){//if the queue is empty
		myqueue->front = myqueue->rear = new_node;
	}
	else{
		myqueue->rear->next = new_node;
		myqueue->rear = new_node;//move queue rear pointer to new_node
	}

	return myqueue;
}

queue *delete_queue(queue *myqueue)
{
	node *p_node = NULL;
	p_node = myqueue->front;
	if (NULL == p_node){
		printf("this is empty queue\n");
		return NULL;
	}
	else{
		myqueue->front = myqueue->front->next;
		if (myqueue->front == NULL){
			myqueue->rear = NULL;
		}
		free(p_node);
	}

	return myqueue;
}

int get_queue_length(queue *myqueue)
{
	node *p_node = NULL;
	int len = 0;

	p_node = myqueue->front;
	if (NULL != p_node){
		len = 1;
	}
	while (p_node != myqueue->rear)
	{
		p_node = p_node->next;
		len++;
	}

	return len;
}

void queue_print(queue *myqueue)
{
	node *p_node = NULL;
	p_node = myqueue->front;

	if (NULL == p_node){
		printf("this is empty queue\n");
		return;
	}
	printf("The queue is :");
	while (p_node != myqueue->rear)
	{
		printf("%2d", p_node->data);
		p_node = p_node->next;
	}
	printf("%2d\n", p_node->data);
}

int main()
{
	queue * myqueue = create_queue();
	insert_queue(myqueue, 2);
	insert_queue(myqueue, 1);
	insert_queue(myqueue, 3);
	insert_queue(myqueue, 9);
	insert_queue(myqueue, 5);
	insert_queue(myqueue, 6);
	int len = get_queue_length(myqueue);
	printf("The queue length is :%d\n", len);
	queue_print(myqueue);

	delete_queue(myqueue);
	len = get_queue_length(myqueue);
	printf("The queue length is :%d\n", len);
	queue_print(myqueue);

	delete_queue(myqueue);
	len = get_queue_length(myqueue);
	printf("The queue length is :%d\n", len);
	queue_print(myqueue);
}