I need a two level priority queue

[User 10395751]

Hey, I need a C code which builds the printer job queue. However, the printer job queue is built as a two level priority queue.

[_Superman_]

Looks like a single linked list. Here is a program for a single link list - Singly linked list[^] You will need to modify the program slightly to cater to your requirement. The given program only uses an integer variable. Instead, you will need to make 2 checks on the userType and the pages.

«_Superman_»  _I love work. It gives me something to do between weekends.

_Microsoft MVP (Visual C++) (October 2009 - September 2013)

Polymorphism in C

[User 10395751]

I used this code.

void enqueue(char type, int p){
struct node *newPtr, *prevPtr, *presentPtr,*tempPresent;

//Allocating memory for new member
newPtr = malloc(sizeof(struct node));

//Checking allocation. If there is not room for new member in RAM then it gives an error
if(newPtr != NULL){
	newPtr->pages = p;
	newPtr->userType = type;
	newPtr->nextPtr = NULL;
	
	prevPtr = NULL;
	presentPtr = front;
	
	while(presentPtr != NULL && type > presentPtr->userType){
		prevPtr = presentPtr;
		presentPtr = presentPtr->nextPtr;
	}
	//Checking if new member is the first element of the linked list or not
	if(prevPtr == NULL){
		newPtr->nextPtr = front;
		front = newPtr;
	}
	else{
		prevPtr->nextPtr=newPtr;
		newPtr->nextPtr=presentPtr;
	}
}//If allocation fails throws a message to the user
else{
	printf("System out of memory!");
}

}

This code moves along first priority. But when I add a page check in this loop then it goes infinite loop. What will be the solution?

while(presentPtr != NULL && type > presentPtr->userType){
prevPtr = presentPtr;
presentPtr = presentPtr->nextPtr;
}

[_Superman_]

Its probably because of an incorrect condition check. Please post the code with the page check that you put in.

«_Superman_»  _I love work. It gives me something to do between weekends.

_Microsoft MVP (Visual C++) (October 2009 - September 2013)

Polymorphism in C

[User 10395751]

I add this one.

while(presentPtr != NULL && type > presentPtr->userType){
prevPtr = presentPtr;
presentPtr = presentPtr->nextPtr;
}

if(type == presentPtr->userType){
while(presentPtr != NULL && p > presentPtr->pages){
prevPtr = presentPtr;
presentPtr = presentPtr->nextPtr;
}
}

[_Superman_]

Logic looks OK. I guess you need to single step through the code using the debugger and find out the issue.

«_Superman_»  _I love work. It gives me something to do between weekends.

_Microsoft MVP (Visual C++) (October 2009 - September 2013)

Polymorphism in C

[User 10395751]

I tried but didn't find the problem. Do you have an idea?

[User 10395751]

Finded it, thanks for your help! :)