队列与循环队列

复习一下队列与循环队列的实现（C语言）

1、单链队列：

 1 typedef struct QNode{ //若不写typedef，在C中每次定义QNode需要在前面加上struct，而C++不必
 2     QElemType data;
 3     struct QNode *next;
 4 }QNode,*QueuePtr;
 5 
 6 typedef struct{ //若不写结构体名，则需要加上typedef
 7     QueuePtr front;
 8     QueuePtr rear;
 9 }LinkQueue;
10 
11 status InitQueue(LinkQueue &Q){  //初始化
12     Q.front = Q.rear = (QueuePtr) malloc(sizeof(QNode));
13     if(!Q.front)
14         exit(OVERFLOW);
15     Q.front -> next = NULL;
16     return OK;
17 }
18 
19 status EnQueue(LinkQueue &Q,QElemType &e){  //把元素e入队
20     p = (QueuePtr) malloc(sizeof(QNode));
21     if(!p)
22         exit(OVERFLOW);
23     p -> next = NULL;
24     p -> data = e;
25     Q.rear -> next = p;
26     Q.rear = p;
27     return OK;
28 }
29 
30 status Dequeue(LinkQueue &Q,QElemType &e){  //删除对头元素，且把队顶元素保存在e中
31     if(Q.front == Q.rear)
32         return ERROR;
33     p = Q.front -> next;
34     e = p -> data;
35     Q.front -> next = p -> next;
36     if(Q.rear == p)
37         Q.rear = Q.front;
38     free(p);
39     return OK;
40 }

2、循环队列

 1 #define MAXQSIZE 100
 2 
 3 typedef struct{
 4     QElemType *base;
 5     int front;
 6     int rear;
 7 }SqQueue;
 8 
 9 status InitQueue(SqQueue &Q){
10     Q.base = (QElemType *) malloc(MAXQSIZE*sizeof(QElemType));
11     if(!Q.base)
12         exit(OVERFLOW);
13     Q.front = Q.rear = 0;
14     return OK;
15 }
16 
17 status EnQueue(SqQueue &Q,QElemType &e){
18     if((Q.rear+1)%MAXQSIZE == Q.front)  //队列已满
19         return ERROR;
20     Q.base[Q.rear] = e;
21     Q.rear = (Q.rear+1)%MAXQSIZE;
22     return OK;
23 }
24 
25 status Dequeue(SqQueue &Q,QElemType &e){
26     if(Q.front == Q.rear)
27         return ERROR;
28     e = Q.base[Q.front];
29     Q.front = (Q.front+1)%MAXQSIZE;
30     return OK;
31 }