两个队列一个程序

Question

I want to create two queues of ordinary and vip clients in a bank, 1.How can i create two queues in one program. 2.How can i pass the structure for queues as parameter of function enqueue and dequeue? I am enquing according to customer type eg i enqueue to queue1 if client is vip i enqueue to queue2 if client is ordinary same for dequeue

#include <stdio.h>
#include <malloc.h>
#include<string.h>

int position=0;
int length=1;enter code here

typedef struct Node
{
    int record;
    int CardNum;
    char CustomerType[20];
    struct Node* next;

}Node;

//VIP QUEUE
typedef struct queue
{
    Node* front1 = NULL;
    Node* rear1 = NULL;
}Queue1;

//Ordinary QUEUE
typedef struct queue
{
    Node* front2 = NULL;
    Node* rear2 = NULL;
}Queue2;

void Enqueue();
void Dequeue();

int main()
{
    char command[10];
    while(scanf("%s",command))
    {
        if(strcmp(command,"IN") == 0)
        {
            printf("IN:");
            Enqueue();
        }
        if(strcmp(command,"LIST") == 0)
        {
            printf("LIST:\n");
            List();
        }
        if(strcmp(command,"OUT") == 0)
        {
            Dequeue();
        }
        if(strcmp(command,"QUIT") ==0)
        {
            printf("GOOD BYE!\n");
            break;
        }
    }
    return 0;
}

Answer 1

Well the thing is you have created two different Queue types. But it shouldn't be the case. After all the queue we use to store VIP's will be same type as that of another. But yes you need two different instance of that Queue type.

Moreover you can't initialize members inside the struct declaration. This won't work.

For passing the Queue to another function there are several ways. You can simply create Queue q1,q2 and then pass it's address to the function to allocate necessary nodes.

typedef struct queue
{
    Node* front;
    Node* rear;
}Queue;

Queue q1,q2;
init(&q1);
init(&q2);
...

void init(Queue *q1){
    q1->front = NULL;
    q2->rear  = NULL;
}

The signature of the init would be

void init(Queue *q);

Whatever I have shown here in init you can do the same with the other queue functions.

In fact moreover you can do pass not the address and then make changes to the local struct instance passed to the function and then return it.

Other points that I can't ignore:

You have used scanf and checked it's return value in one way - do it proper way.

while(scanf("%9s",command) == 1){
   ...

Also another point is using multiple if with same condition. You should merge the if statements - saves you from repetitive code and also you are not doing a redundant check.

---

You could have initialized the structure like this also (But I have shown the other way so that you can write the other queue functions).

Queue q1 = { .front = NULL, .rear = NULL };

Also another thing the signature for the main should be int main(void) .