Thread: Shifting arrays K positions without using additional memory

I have been tasked with a program that shifts an array k position without additional memory. I don't know what kind of memory are they talking about, because I will obviously have to use one index value for the loop... Anyway, here is an example:
shiftArray(numbers, k) for 1 2 3 4 5 6 7 8 and k = 3 should give: 4 5 6 7 8 1 2 3.

The problem is simple, however, after constantly failing at minor things, I cannot think clear anymore. Here is my full code. The result for 1 2 3 4 5 6 7 8 is 5 2 3 4 5 6 7 8. I have discovered that the problem is in the if statement, but I cannot figure out why. I know the code is cluttered for the function, but that is only because I do not want to store the size into a variable, because of that memory condition...

If you cannot find a way around the program, could you give me another suggestion if there is a more efficient way? Thank you very much.

Cosmin

Code:

#include <iostream>

using namespace std;

void shiftArray(int numbers[], int k)
{
	int index;
	for(index = 0; index < (int)(sizeof numbers)/(sizeof numbers[0]);  index++)
	{
		if(index >= numbers[(int)(sizeof numbers)/(sizeof numbers[0]) - k])
		{
			numbers[index] = numbers[index % k];
		}
                                else
                                {
                                                numbers[index] = numbers[index + k];
                                }
	}
}

int main(int argc,char* argv) 
{
	int numbers[] = {1, 2, 3, 4, 5, 6, 7, 8};
	int k = 4;
	shiftArray(numbers, k);
	int i;
	for(i = 0; i < (int)(sizeof numbers)/(sizeof numbers[0]); i++)
	{
		cout << numbers[i] << " ";
	}
	cout << endl;

	return 0;
}

The shiftArray function cannot do sizeof(numbers). You need to pass the size of the array to the function:

Code:

void shiftArray(int numbers[], size_t array_size, int k)

Does "no additional memory" mean that you can't even use a single temporary variable?

Hahaha... For showing only, you can do;

Code:

for(int i=k;i<lengthOfArray;i++)
{
cout<<numbers[i];
}
for(int j=0;j<k;j++)
{
cout<<numbers[j];
}

But that's only for display. I know you actually mean, shifting, i am thinking .............

I want to ask one thing, that you aren't allowed to use even a single variable except the specified ones?

I think you will have to use one temporary variable.

Now simple do;

Code:

int temp=0;
for(int index=0;index<k;index++)
{
temp=numbers[k];
numbers[k]++=numbers[index];
numbers[index]=temp;
}

Yes my typing mistake. it will be numbers[k++]. Sorry.