It is just not clicking in my head (Output an array via pointer in reverse)

So this is one of thoose things that is not clicking in my head.

I am trying to write a function using "pointer notation" that will write out the elements of an array of int in reverse order. I know this has to be done via a for loop but I am a little lost when it comes to the "pointer notation". When assinging the address of a pointer to an array it assigns it to the first element [0] correct? Anyways I would appreciate it if someone could offer up and example.

Thanks

Chad

for ( p = &array[n-1] ; p >= array ; p-- )

Quote:

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Originally Posted by Salem

for ( p = &array[n-1] ; p >= array ; p-- )

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What are the declarations in this? Is p the pointer?

So p = the address of the array, correct?

What is n? The element of the array?

Why n - 1? This has something to do with the fact that arrays actually start at 0 correct?


Thanks

Chad

So p = the address of the array, correct?
p is a pointer to an element of the array. If you have T array[n] then it's T *p

Quote:

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Why n - 1? This has something to do with the fact that arrays actually start at 0 correct?

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Exactly:

Code:

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int a[10];
/* printf("%i\n", a[10]); /* out of bounds */
printf("%i\n", a[9]); /* 9 is the last element . . . n (10) - 1 */

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Quote:

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What are the declarations in this?

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They were left out for brevity.

n=size of the array. If you have the array:

Code:

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int myArray[] = {10, 20, 30};

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the size of the array is 3 but the valid index numbers are:

myArray[0] = 10
myArray[1] = 20
myArray[2] = 30

An array name is like a pointer to the first element. So, you can set a pointer to the first element like this:

Code:

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int* p = myArray;
cout<<*p<<endl; //10

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Or, you can set the pointer to point to other elements of the array:

Code:

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p = &myArray[2]; //"p is equal to the address of myArray[2]"
cout<<*p<<endl; //30

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Pointer arithmetic allows you to move the pointer along the array with the increment operator(++) or the decrement operator(--). Since you want to output the elements in reverse order, setting a pointer to the end of the array, and then decrementing that pointer everytime through a for-loop to move it along the array seems like a good approach.