Thread: Array manipulation Question

Ok so i'm writing a program to sort an array using heap sort. I have my main function that gets the information on what the array is, then using a function to sort it. The function is defined as: void maxheapify(int A[], int i, int len)

So I've figured out that the array doesn't really get modified when I pass the array into the function. But I can't just do A=maxheapify(A, i, len) either because in maxheapify A is an int*... And if I turn the A in main to an int* then I get a whole crap load of errors....

So anyone have any suggestions? I can post my whole code if need be.

I printed out the array before and after and it comes out the same.... (not sorted)

Code:

#include <iostream>
#include <iomanip>
#include <cstdlib>

using namespace std;


int operationsCounter=0;

void maxheapify(int A[], int i, int len)
{
	int l=2*i;
	int r=2*i+1;
	int largest, exchange;
	if ((l<=len) && (A[l]>A[i]))
	    {
		largest=l;
		operationsCounter++;
	    }
	else
	    {
		largest=i;
		operationsCounter++;
	    }
	operationsCounter++;
	if ((r<=len) && (A[r]>A[largest]))
	    {
		largest=r;
		operationsCounter++;
	    }
	operationsCounter++;
	if (largest!=i)
	{
		exchange=A[largest];
		A[largest]=A[i];
		A[i]=exchange;
		maxheapify(A, largest, len);
		operationsCounter+=4;
	}
	operationsCounter++;
        //return (A);
}

int main()
{
  int exchange, len, option, fakelen;
  cout << "How big of an array do you want to sort? " << endl;
  cin >> len;
  int A[len];
  cout << "To have " << len << " numbers generated randomly please enter 1, to enter the array yourself please enter 2: " << endl;
  cin >> option;
  if (option == 1)
    {
      for (int i=0; i<len; i++)
	{
	  A[i]=rand();
	  operationsCounter++;
	}
    }
  else if (option == 2)
    {
      cout << "Enter the array: " << endl;
      for (int i=0; i<len; i++)
	{
	  cin >> A[i];
	  operationsCounter++;
	}
    }
  else
    {
      cout << "You didn't enter 1 or 2.  What a fool. Restart the program if you must." << endl;
    }
  cout << "The array before sorting: ";
  for(int i=0; i<len; i++)
    cout << A[i] << " ";
  cout << endl;
  fakelen=len;
  for(int i=len; i>1; i--)
    {
      fakelen--;
      exchange=A[1];
      A[1]=A[i];
      A[i]=exchange;
      maxheapify(A, 1, fakelen);
    }
  cout << "The array after sorting: ";
  for(int i=0; i<len; i++)
    cout << A[i] << " ";
  cout << endl << "The approximate number of operations for an array of size " << len << " is: " << operationsCounter << endl;
  return 0;
}

why? is that not how you declare arrays in c++? It compiles fine and takes in the numbers and prints them out....

compiles fine for me using gcc.... so then how am i supposed to declare it?

why do i have to use one of those? couple sites i've looked at said the way I did is the way to do it.... why shouldn't it work and how exactly do i declare it? int[] A = new int A[len] or something like that?

oh ya.... lol... 1 is supposed to be 0.... let me change that....