数据结构 C 代码 链队列与循环队列

队列是一种特殊的线性表，特殊之处在于它只允许在表的前端（front）进行删除操作，而在表的后端（rear）进行插入操作，和栈一样，队列是一种操作受限制的线性表。进行插入操作的端称为队尾，进行删除操作的端称为队头。

1.队列先进先出，栈先进后出。
2.对插入和删除操作的限定不同。
3.栈是限定只能在表的一端进行插入和删除操作的线性表。
4.队列是限定只能在表的一端进行插入，在另一端进行删除操作的线性表。

• 定义

//链队列的节点
typedef struct LinkNode{
	int data;
	LinkNode* next;
}*LinkNodePtr;

//链队列
typedef struct LinkQueue{
	LinkNodePtr front;
	LinkNodePtr rear;
}*LinkQueuePtr;

• 初始化

//Construct an empty queue
LinkQueuePtr initQueue(){
	LinkQueuePtr resultPtr = (LinkQueuePtr)malloc(sizeof(struct LinkQueue));
	//The header, the data is not useful.
	LinkNodePtr headerPtr = (LinkNodePtr)malloc(sizeof(struct LinkNodePtr));
	headerPtr->next = NULL;
	
	resultPtr->front = headerPtr;
	resultPtr->rear = headerPtr;
	return resultPtr;
}

// Output the queue.

void outputLinkQueue(LinkQueuePtr paraQueuePtr){
	LinkNodePtr tempPtr = paraQueuePtr->front->next;
	while (tempPtr != NULL) {
		printf("%d ", tempPtr->data);
		tempPtr = tempPtr->next;
	}//Of while
	printf("rn");
}

• 入队

//Enqueue.

void enqueue(LinkQueuePtr paraQueuePtr, int paraElement) {
	//Step 1. Create a new node
	LinkNodePtr tempNodePtr = (LinkNodePtr)malloc(sizeof(struct LinkNode));
	tempNodePtr->data = paraElement;
	tempNodePtr->next = NULL;
	
	//Step 2. Link to the existing rear
	paraQueuePtr->rear->next = tempNodePtr;
	
	//Step 3. It is the new rear
	paraQueuePtr->rear = tempNodePtr;
}

• 出队

// Dequeue.

int dequeue(LinkQueuePtr paraQueuePtr) {
	int resultValue;
	LinkNodePtr tempNodePtr;

	//Step 1. Is the queue empty?
	if (paraQueuePtr->front == paraQueuePtr->rear) {
		printf("The queue is empty.rn");
		return -1;
	}//Of if

	//Step 2. Change the queue.
	tempNodePtr = paraQueuePtr->front->next;
	resultValue = tempNodePtr->data;
	paraQueuePtr->front->next = paraQueuePtr->front->next->next;

	if (paraQueuePtr->rear == tempNodePtr) {
		paraQueuePtr->rear = paraQueuePtr->front;
	}//Of if

	//Step 3. Free space.
	// free(tempNodePtr);
	tempNodePtr = NULL;

	//Step 4. Return.
	return resultValue;
}

• 测试代码

//Unit test.

void testLinkQueue(){
	LinkQueuePtr tempQueuePtr;
	tempQueuePtr = initQueue();
	enqueue(tempQueuePtr, 10);
	enqueue(tempQueuePtr, 30);
	enqueue(tempQueuePtr, 50);

	outputLinkQueue(tempQueuePtr);

	printf("dequeue gets %drn", dequeue(tempQueuePtr));
	printf("dequeue gets %drn", dequeue(tempQueuePtr));
	printf("dequeue gets %drn", dequeue(tempQueuePtr));
	printf("dequeue gets %drn", dequeue(tempQueuePtr));

	enqueue(tempQueuePtr, 8);
	outputLinkQueue(tempQueuePtr);
}

//The entrance.

int main(){
	testLinkQueue();
	return 1;
}

#include 
#include 

#define TOTAL_SPACE 5

// Circle int queue.

typedef struct CircleIntQueue{
	int data[TOTAL_SPACE];

	int head;

	int tail;
}*CircleIntQueuePtr;

// Initialize the queue.

CircleIntQueuePtr initQueue() {
	CircleIntQueuePtr resultPtr = (CircleIntQueuePtr)malloc(sizeof(struct CircleIntQueue));
	resultPtr->head = 0;
	resultPtr->tail = 0;

	return resultPtr;
}// Of the first constructor


void enqueue(CircleIntQueuePtr paraPtr, int paraValue) {
	if ((paraPtr->tail + 1) % TOTAL_SPACE == paraPtr->head) {
		printf("Queue full.rn");
		return;
	} // Of if

	paraPtr->data[paraPtr->tail % TOTAL_SPACE] = paraValue;
	paraPtr->tail++;
}// Of enqueue


int dequeue(CircleIntQueuePtr paraPtr) {
	int resultValue;
	if (paraPtr->head == paraPtr->tail) {
		printf("No element in the queue.rn");
		return -1;
	} // Of if

	resultValue = paraPtr->data[paraPtr->head % TOTAL_SPACE];
	paraPtr->head++;

	return resultValue;
}

//Output the queue.

void outputLinkQueue(CircleIntQueuePtr paraPtr){
	int i;
	if (paraPtr->head == paraPtr->tail) {
		printf("Empty queue.");
		return;
	} // Of if

	printf("Elements in the queue: ");
	for (i = paraPtr->head; i < paraPtr->tail; i++) {
		printf("%d, ", paraPtr->data[i % TOTAL_SPACE]);
	} // Of for i

	printf("rn");
}

//Unit test.

void testLinkQueue(){
	int i = 10;
	CircleIntQueuePtr tempPtr = initQueue();
	for (; i < 16; i ++) {
		enqueue(tempPtr, i);
	}//Of for i

	outputLinkQueue(tempPtr);

	for (i = 0; i < 6; i ++) {
		printf("dequeue gets %drn", dequeue(tempPtr));
	}//Of for i

	enqueue(tempPtr, 8);
	outputLinkQueue(tempPtr);
}

//The entrance.

int main(){
	testLinkQueue();
	return 1;
}