Need Help With Recursive Functions

jonas12rena · #1 31-Jul-2006, 08:42

Here is my code:

CPP / C++ / C Code:

void Clueless (int A[], int size)
{
      if(size > 0){A[0] = 0; Clueless (A+1, size -1);}
}

I am having trouble figuring out what this code does. With my limited knowledge of reading code(correct me if I am wrong) If the integer size is larger than zero the first element of A will be set to zero, then recursion calls the Clueless function again and sets the pointer to first element to -1(isnt this the final number in the array?) So will the recursive function set just the first element to zero, or will it set the last element to zero, or will all elements be set to zero, or finally wil it create a infinite loop?

WaltP · #2 31-Jul-2006, 11:12

Quote:

Originally Posted by jonas12rena

Here is my code: (reformatted for readability -- wp)

CPP / C++ / C Code:

void Clueless (int A[], int size)
{
    if (size > 0)
    {
        A[0] = 0; 
        Clueless (A+1, size -1);
    }
}

I am having trouble figuring out what this code does. With my limited knowledge of reading code(correct me if I am wrong) If the integer size is larger than zero the first element of A will be set to zero, then recursion calls the Clueless function again and sets the pointer to first element to -1(isnt this the final number in the array?) So will the recursive function set just the first element to zero, or will it set the last element to zero, or will all elements be set to zero, or finally wil it create a infinite loop?

Close.

This function zeros an array of size elements.

In effect:

Code:

As long as size is not zero
    Zero the first element of the array
    Call the function again with
        address of next element
        size - 1

The address of the next element becomes the start of the array in the next function call. And size reflects the fact that there is one element gone (from the front of the array) -- which the next call knows nothing about.

Before the if you can put print/cout statements to see exactly what each call of the function sees.

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Need Help With Recursive Functions

Re: Need Help With Recursive Functions