3:4循环队列

创建循环队列

typedef struct CircleIntQueue{
    
    int data[TOTAL_SPACE];
    int head;
    int tail;
    
}*CircleIntQueuePtr;

初始化队列

CircleIntQueuePtr initQueue(){
    
    CircleIntQueuePtr resultPtr = (CircleIntQueuePtr)malloc(sizeof(CircleIntQueue));
    
    //起始位为0
    resultPtr->head = 0;
    resultPtr->tail = 0;

    return resultPtr;
}

添加元素

void enqueue(CircleIntQueuePtr paraPtr, int paraValue){
    
    //判断循环链表是否已满（最后位置即队头前不放元素）
    if((paraPtr->tail + 1) % TOTAL_SPACE == paraPtr->head % TOTAL_SPACE){
        printf("Queue full.rn");
        return;
    }

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

删除元素并返回元素

int dequeue(CircleIntQueuePtr paraPtr){
    
    //判断链表是否为空
    if(paraPtr->head == paraPtr->tail){
        printf("No element in the queue.rn");
        return -1;
    }
    
    int resultValue;

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

    return resultValue;
}

打印链表

void outputLinkQueue(CircleIntQueuePtr paraPtr){
    
    if (paraPtr->head == paraPtr->tail){
        printf("Empty queue.");
        return;
    }
    
    int i;
    
    printf("Elements in the queue: ");
    for (i = paraPtr->head; i < paraPtr->tail; i++){
        printf("%d, ", paraPtr->data[i % TOTAL_SPACE]);
    }

    printf("rn");
}

• CircleIntQueuePtr initQueue()

CircleIntQueuePtr tempPtr = initQueue();

• void enqueue(CircleIntQueuePtr paraPtr, int paraValue)

enqueue(tempPtr, i);

• int dequeue(CircleIntQueuePtr paraPtr)

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

enqueue(tempPtr, 8);
enqueue(tempPtr, 9);

//
//  main.c
//
//  Created on 2022/5/16.
//


#include 
#include 

#define TOTAL_SPACE 5

//创建循环队列
typedef struct CircleIntQueue{
    
    int data[TOTAL_SPACE];
    int head;
    int tail;
    
}*CircleIntQueuePtr;

//初始化队列
CircleIntQueuePtr initQueue(){
    
    CircleIntQueuePtr resultPtr = (CircleIntQueuePtr)malloc(sizeof(CircleIntQueue));
    
    //起始位为0
    resultPtr->head = 0;
    resultPtr->tail = 0;

    return resultPtr;
}

//添加元素
void enqueue(CircleIntQueuePtr paraPtr, int paraValue){
    
    //判断循环链表是否已满（最后位置即队头前不放元素）
    if((paraPtr->tail + 1) % TOTAL_SPACE == paraPtr->head % TOTAL_SPACE){
        printf("Queue full.rn");
        return;
    }

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

//删除元素并返回元素
int dequeue(CircleIntQueuePtr paraPtr){
    
    //判断链表是否为空
    if(paraPtr->head == paraPtr->tail){
        printf("No element in the queue.rn");
        return -1;
    }
    
    int resultValue;

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

    return resultValue;
}

//打印链表
void outputLinkQueue(CircleIntQueuePtr paraPtr){
    
    if (paraPtr->head == paraPtr->tail){
        printf("Empty queue.");
        return;
    }
    
    int i;
    
    printf("Elements in the queue: ");
    for (i = paraPtr->head; i < paraPtr->tail; i++){
        printf("%d, ", paraPtr->data[i % TOTAL_SPACE]);
    }

    printf("rn");
}

//测试
void testLinkQueue(){
    
    int i = 10;
    CircleIntQueuePtr tempPtr = initQueue();
    for (; i < 16; i++){
        enqueue(tempPtr, i);
    }
    
    outputLinkQueue(tempPtr);
    
    for (i = 0; i < 6; i++){
        printf("dequeue gets %drn", dequeue(tempPtr));
    }
    
    enqueue(tempPtr, 8);
    outputLinkQueue(tempPtr);
    enqueue(tempPtr, 9);
    outputLinkQueue(tempPtr);
}

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

在循环队列中，当队列为空时，有front=rear，而当所有队列空间全占满时，也有front=rear。

为了区别这两种情况，规定循环队列最多只能有TOTAL_SPACE-1个队列元素，当循环队列中只剩下一个空存储单元时，队列就已经满了。