链表实现队列

上篇博客是用顺序表实现队列, 现在用双向带头结点带环链表实现对队列的出队列, 入队列, 取队首元素, 以及销毁队列的相关操作

1.初始化链表

void DLinkQueInit(DLinkQue** q)
{if(q == NULL){return;//非法输入}if(*q == NULL){return;//非法输入带头结点的链表至少有一个傀儡结点}*q = (DLinkQue*)malloc(sizeof(DLinkQue));(*q) -> next = *q;(*q) -> prev = *q;(*q) -> data = 0;
}

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2.入队列

void DLinkQuePush(DLinkQue* q, DLinkQueType value)
{if(q == NULL){return;//非法输入}DLinkQue* new_node = DLinkQueCreatNewNode(value);DLinkQue* prev = q -> prev;prev -> next = new_node;new_node -> prev = prev;new_node -> next = q;q -> prev = new_node;
}

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3. 出队列

void DLinkQuePop(DLinkQue* q)
{if(q == NULL){return;//非法输入}if(q -> next == NULL){return;//非法输入带头结点的链表至少有一个傀儡结点}if(q -> next == q){return;//空队列}DLinkQue* to_delete = q -> next;DLinkQue* next = to_delete -> next;q -> next = next;next -> prev = q;DLinkQueDestroyNode(to_delete);to_delete = NULL;
}

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4. 取队首元素

int DLinkStackGetFront(DLinkStack* stack, DLinkStackType* value)
{if(stack == NULL){return -1;//非法输入}if(stack -> next == stack){return -1;//空栈}*value = (stack -> prev) -> data;return 0;
}int DLinkStackSize(DLinkStack* stack)
{if(stack == NULL){return 0;//非法输入}if(stack -> next == stack){return 0;//非法输入}DLinkStack* cur = stack -> next;int size = 0;for(; cur != stack; cur = cur -> next){size++;}return size;
}

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5. 销毁队列

void DLinkQueDestroy(DLinkQue** q)
{if(q == NULL){return;//非法输入}if(*q == NULL){return;//非法输入带头结点的链表至少有一个傀儡结点}int i = DLinkQueSize(*q);DLinkQue* to_delete;DLinkQue* next;for(; i > 0; i--){//DLinkQuePop(*q);to_delete = (*q) -> next;next = to_delete -> next;(*q) -> next = next;next -> prev = *q;DLinkQueDestroyNode(to_delete);to_delete = NULL;}DLinkQueDestroyNode(*q);*q = NULL;
}