Thread: Circular queue base on struct.

  1. #1
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    Post Circular queue base on struct.

    Hi. Iam stuck with how to make a circular queue that are based on a struct. Have been reading about the implementation but cant really understand it fully.

    Here is what i got so far.

    Code:
    #define SIZE 10
    typedef struct
    {
        char reg;
        char brand;
        int modelyear;
        int mileage;
    }car;
    
    typedef struct
    {
        struct *car_queue;
        int start;
        int stop;
    }circular;
    
    car keyinput();
    
    
    int main(int argc, char **argv)
    {
        int i;
        car item[SIZE];
        
        printf("Add %d cars to the que.\n\n",SIZE);
        for(i=0;i<SIZE;i++){
            item[i]=keyinput();
        }
        return 0;
    }
    
    
    car keyinput()
    {
        car item1;
    
    
        puts("Number:");
        scanf("%s",item1.reg);
        fflush(stdin);
        puts("");
        puts("Brand:");
        scanf("%s",item1.brand);
        fflush(stdin);
        puts("");
        puts("Modelyear:");
        scanf("%d",&(item1.modelyear));
        fflush(stdin);
        puts("");
        puts("Milage:");
        scanf("%d",&(item1.milage));
        fflush(stdin);
    
    
        return item1;
    }
    Whould be nice with some help here.

  2. #2
    Registered User camel-man's Avatar
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    First step is turn up your compiler warnings.

  3. #3
    Hurry Slowly vart's Avatar
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    All problems in computer science can be solved by another level of indirection,
    except for the problem of too many layers of indirection.
    David J. Wheeler

  4. #4
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    Is the circular struct supposed to have a pointer to the array? Currently, the pointer in the circular struct has bad syntax. The circular structure should have a member called "size" so the code knows when to "wrap around" from the end of the array to the beginning of the array.

  5. #5
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    Have made some changes.

    Quote Originally Posted by camel-man View Post
    First step is turn up your compiler warnings.
    I have been fixing some code that didnt seem so right.
    First i have changed "struct *car_queue" to "car *car_queue[QUE_SIZE]" and after that i added this to the main, "circular que".

    So now i tried to add this for my forloop:
    "que.car_queue[i]=input();" then i got an error so then i thougth that i can have a "->" instead of "."

    Now when i did this i get this error:

    "invalid type argument of '->' (have 'circular')"

    So what does it mean. I get that i does not want me to use "->"
    do it want me to have 'circular' but what does it really mean.

  6. #6
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    I posted an answer to that just now. Changed the struct to this:
    Code:
    typedef struct
    {
        char reg[25];
        char brand[25];
        int modelyear;
        int mileage;
    }car;
    
    
    typedef struct
    {
        car *car_queue[QUE_SIZE];
        int start;
        int stop;
        
    }circular;
    added "circular que" to main.

  7. #7
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    car *car_queue[QUE_SIZE] is an array of pointers to struct car. I think what you want is a single pointer to struct car, which would be a pointer to the first element of the array (which would be a pointer to the array).

  8. #8
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    Quote Originally Posted by rcgldr View Post
    car *car_queue[QUE_SIZE] is an array of pointers to struct car. I think what you want is a single pointer to struct car, which would be a pointer to the first element of the array (which would be a pointer to the array).
    So what you are saying that is I should have a pointer like this "car *car_queue".

  9. #9
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    Quote Originally Posted by Mogren3000 View Post
    So what you are saying that is I should have a pointer like this "car *car_queue".
    Yes, that would be a pointer to the first member of an array of struct cars.

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