Stealthgerbil posted:

I have an assignment where I had to make a queue (without using the STL ) using a linked list. The queue class I made is supposed to represent an airport in the assignment and the nodes are the planes, ect. That part works fine and I can remove and add 'planes' perfectly.

However the second part is driving me nuts. Pretty much for the second part of the assignment I need to turn the three queues into a single queue, based on whichever queue has the highest 'passenger' integer. The story is that the airport got snowed in but they have a reserve runway to use and are letting planes from the other three runways go, depending on which has the highest amount of passengers.

I was messing around trying to figure something out and I did manage to make a function that calls the three queues by reference and then compares the queues to see which one has the highest 'passenger' integer. It also returns a value of 1, 2, or 3, depending on which queue it came from. Then in the main, I have some if/else statements which calls the remove function for whichever queue that the integer returned refers to.

However here is my problem. Once all of the nodes in the queue are removed, I get an exception error because I am still calling the three queues by reference in my function that checks to see which queue has the highest 'passenger' integer. Because of that, it tries to read information from a null queue and crashes.

Is there a way to get the function to ignore an empty queue? The program would work fine if it wasn't for this (it does function perfectly until one of the queues is empty). I can definitely post (on pastebin) my terrible mess of code if anyone is interested.

edit: or any other suggestions are welcome. I dont mind completely redoing the code if it makes sense.

Stealthgerbil posted:

edit: or any other suggestions are welcome. I dont mind completely redoing the code if it makes sense.

Nomnom Cookie posted:

Your code is using O(n*log(n)) space. Mergesort is an O(n) space algorithm.

kingcrimbud posted:

Last i checked big O dealt with time and not space.

kingcrimbud posted:

Well that's Interesting. And what is space? Is that the memory i'm using? Last i checked big O dealt with time and not space. I may not know c++ but please don't question my algorithms.

kingcrimbud posted:

Well that's Interesting. And what is space? Is that the memory i'm using? Last i checked big O dealt with time and not space. I may not know c++ but please don't question my algorithms.

quote:

Worst case space complexity: Θ(n)

Lexical Unit posted:

We are getting trolled so hard right now.

kingcrimbud posted:

Well that's Interesting. And what is space? Is that the memory i'm using? Last i checked big O dealt with time and not space. I may not know c++ but please don't question my algorithms.

kingcrimbud posted:

code:

int randomPartition(float A[], int p, int r)
{
	...
	i = A[rand() % sizeof(A)];
	...
}

Bhaal posted:

1) sizeof returns the total size of the array, so sizeof(float[10]) is going to be 40 for a 4 byte float. Better approaches are to use sizeof(array)/sizeof(<type>), or better yet, keep track of a given array's size in an integer and just use that to grab a random element, etc.

2) sizeof (to my knowledge) is calculated at compile time and I was pretty sure a dynamically allocated array being sizeof'd throws a compiler error. Maybe I'm wrong on that but either way that's the first thing I'd look at re: crashing.

UberJumper posted:

A question about time. Basically i am working on my game and want to store the current hour/minute/second of the ingame time. I have a timer that currently returns the timedelta(ms) between updates.

E.g:

m_CurrentMilliseconds = (Timer::GetTimeDelta() * m_Rate);

Is there something better then me doing the conversions manually by myself?

kingcrimbud posted:

code:

/* Partition Procedure */
int Partition(float A[], int p, int r)
{
	printf("Partition Procedure");
	x=A[r];
	i2=p-1;
	for(j=p;j=r-1;j++)
	{
		if(A[j] <= x)
		{
			i2=i2+1;
			temp2=A[i2];
			A[i2]=A[j];
			A[j]=temp2;
		}
	}
	temp3=A[i2+1];
	A[i2+1]=A[r];
	A[r]=temp3;
	return i2+1;
}

Veritron posted:

i know there's some kind of tacit agreement to ignore you going on here, but you are like some kind of reverse genius

Veritron posted:

i know there's some kind of tacit agreement to ignore you going on here, but you are like some kind of reverse genius

ctz posted:

please don't question my algorithms

Lexical Unit posted:

I'm trying to track down a viral #define someone introduced into the nightmare that is our codebase. What trick can I use to figure out where the #define is located?

Lexical Unit posted:

I'm trying to track down a viral #define someone introduced into the nightmare that is our codebase. What trick can I use to figure out where the #define is located?

Zakalwe posted:

grep -R \#define | grep FOO

Lexical Unit posted:

Our build system sucks so much oh god.

mincepiesupper posted:

I have a question about debugging vectors: I recently had to change stl header files in order to make the use of the [] operator behave more like at() and tell me when indices went beyond the size of the vector. Is there a way I could have done this without changing the header files? I'm using gcc 4.1.

Also, I wasn't able to get any output which told me where exactly the error was as any assert I added reported the error in the stl header file not the code that was using an invalid index.

mincepiesupper posted:

Will this work with a release build? The code I am having the problem with is not mine, what I've been given to build it with is for release builds only. I've also been told that debug builds don't work but I've not yet tried this to see exactly what 'don't work' means.

Avenging Dentist posted:

const char *

RussianManiac posted:

That is not what I want. I want a wrapper around char that will act like normal std::string in most ways except that it would share underlying char * with other strings and substr operation would be really fast on it.

Contero posted:

Is there a sign function? i.e. sign(-2.3) -> -1

I've always just done val/abs(val), but this is a little gross / bad if val == 0.

Contero posted:

Is there a sign function? i.e. sign(-2.3) -> -1

I've always just done val/abs(val), but this is a little gross / bad if val == 0.

RussianManiac posted:

quote:

Am I better off implementing my own immutable string class?

tef posted:

http://en.wikipedia.org/wiki/Rope_(computer_science)

If you have large strings you may find ropes to be a useful representation of them


Signs point to no.

RussianManiac posted:

This would be a lot worse for my problem, as substring takes logarithmic time using ropes and using immutable string it will be constant. Oh well, I guess I will just implement my own very simple immutable string class. All I have is just a giant string that never changes, and a bunch of operations that work and/or return with substrings of this immutable string.