数据结构：2.7 队列的顺序存储和链式存储

//顺环队列  头出尾进

#define MaxSize 100

struct QNode {
    ElementType Data[MaxSize];
    int rear;  //尾
    int front;  //头
};
typedef struct QNode *Queue;

//入队列
void AddQ ( Queue PtrQ, ElementType item ) {
    if ( (PtrQ->rear+1) % MaxSize == PtrQ->front ) {
        printf("队列满");
        return;
    }
    PtrQ->rear = (PtrQ->rear+1) % MaxSize; //移尾
    PtrQ->Data[PtrQ->rear] = item;  //入队
}

//出队列
ElementType DeleteQ ( Queue PtrQ ) {
    if ( PtrQ->front == PtrQ->rear ) {
        printf("队列空");
        return ERROR;
    }
    else {
        PtrQ->front = (PtrQ->front+1) % MaxSize;
        return PtrQ->Data[PtrQ->front];
    }
}

struct Node {
    ElementType Data;
    struct Node *Next;
};

struct QNode {
    struct Node *rear;
    struct Node *front;
};
typedef struct QNode *Queue;
Queue PtrQ;

//出队
ElementType DeleteQ ( Queue PtrQ ) {
    struct Node *FrontCell;
    ElementType FrontElem;
    
    if ( PtrQ->front == NULL ) {
        printf("队列空"); return ERROR;
    }
    FrontCell = PtrQ->front;
    if ( PtrQ->front == PtrQ->rear )  //队列只有一个元素
        PtrQ->front = PtrQ->rear = NULL;
    else 
        PtrQ->front = PtrQ->front->Next;
    FrontElem = FrontCell->Data;
    free(FrontCell);
    return FrontElem;
}