数据结构 C 代码 3.6: 链队列

摘要: 队列的提出, 也是想获得 O ( 1 ) O(1) O(1) 的时间复杂度.

先上代码, 再说废话.

#include 
#include 


typedef struct LinkNode{
	int data;
	LinkNode* next;
}*LinkNodePtr;


typedef struct LinkQueue{
	LinkNodePtr front;
	LinkNodePtr rear;
}*LinkQueuePtr;


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


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


void enqueue(LinkQueuePtr paraQueuePtr, int paraElement) {
	//Step 1. Create a new node
	LinkNodePtr tempNodePtr = (LinkNodePtr)malloc(sizeof(LinkNodePtr));
	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;
}//Of enqueue


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;
}//Of enqueue
	

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);
}//Of testLinkQueue
 

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

10 30 50
dequeue gets 10
dequeue gets 30
dequeue gets 50
The queue is empty.
dequeue gets -1
8
Press any key to continue

1. 用到了一个头结点, 一个头指针，一个尾指针.
2. 判断队列是否为空, 只需要看头指针是否等于尾指针.
3. 为啥不让我 free?

#include 
#include 


typedef struct LinkNode{
	int data;
	LinkNode* next;
}*LinkNodePtr;


typedef struct LinkQueue{
	LinkNodePtr front;
	LinkNodePtr rear;
}*LinkQueuePtr;


LinkQueuePtr initQueue(){
	LinkQueuePtr resultPtr;
	printf("In initQueue, the address of resultPtr is %drn", &resultPtr);
	resultPtr = (LinkQueuePtr)malloc(sizeof(LinkQueue));
	printf("The value of resultPtr is %drn", resultPtr);
	//The header, the data is not useful.
	LinkNodePtr headerPtr;
	printf("The address of headerPtr is %drn", &headerPtr);
	headerPtr = (LinkNodePtr)malloc(sizeof(LinkNodePtr));
	printf("The value of headerPtr is %drn", headerPtr);
	headerPtr->next = NULL;
	
	resultPtr->front = headerPtr;
	resultPtr->rear = headerPtr;
	return resultPtr;
}//Of initQueue


void outputLinkQueue(LinkQueuePtr paraQueuePtr){
	LinkNodePtr tempPtr;
	printf("In printLinkQueue, the address of tempPtr is %drn", &tempPtr);
	tempPtr = paraQueuePtr->front->next;
	printf("The value of tempPtr is %drn", tempPtr);
	printf("This is a queue: "); 
	while (tempPtr != NULL) {
		printf("%d ", tempPtr->data);
		tempPtr = tempPtr->next;
		printf("The value of tempPtr is %drn", tempPtr);
	}//Of while
}//Of outputLinkQueue


void enqueue(LinkQueuePtr paraQueuePtr, int paraElement) {
	//Step 1. Create a new node
	LinkNodePtr tempNodePtr;
	printf("In linkEnqueue, the address of tempNodePtr is %drn", &tempNodePtr);

	tempNodePtr = (LinkNodePtr)malloc(sizeof(LinkNodePtr));
	printf("The value of tempNodePtr is %drn", tempNodePtr);
	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;
}//Of enqueue


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

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

	//Step 2. Change the queue.
	printf("dequeue test 2rn");
	tempNodePtr = paraQueuePtr->front->next;
	resultValue = tempNodePtr->data;
	paraQueuePtr->front->next = paraQueuePtr->front->next->next;

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

	printf("dequeue test 3, the ptr is %drn", tempNodePtr);
	//Step 3. Free space.
	//free(tempNodePtr);

	//Step 4. Return.
	printf("trying to dequeue %drn", resultValue);
	return resultValue;
}//Of enqueue
	

void testLinkQueue(){
	printf("Start testing.");
	LinkQueuePtr tempQueuePtr;
	tempQueuePtr = initQueue();
	enqueue(tempQueuePtr, 10);
	enqueue(tempQueuePtr, 30);
	enqueue(tempQueuePtr, 50);

	printf("Before outputLinkQueue.rn");
	outputLinkQueue(tempQueuePtr);
	printf("After outputLinkQueue.rn");

	printf("dequeue gets %d", dequeue(tempQueuePtr));
	printf("dequeue gets %d", dequeue(tempQueuePtr));
	printf("dequeue gets %d", dequeue(tempQueuePtr));
	printf("dequeue gets %d", dequeue(tempQueuePtr));
}//Of testLinkQueue
 

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

运行本程序，画出内存使用示意图，并回答如下问题：

1. 运行过程中，哪些变量分配在相邻的空间？
2. 局部变量的空间能否重复利用？举例说明。
3. 指针的地址和值的区别是什么？