CODEWITHSUNDEEP
c++arrays
soniccool
soniccool

Reputation: 6058

Outputted array values different from the values stored

I made an array and set the values from 1 to 9 in the initializeBoard function, but for some reason when I print the values they come out 0 to 8. Why is this happening? Shouldn't it print out 1 to 9 since those are the numbers I put in the array in initializeBoard?

int main()
{
    initializeBoard();
    ticTacToeBoard();
}

void initializeBoard()
{
    for (int i = 1; i < 9; i++)
        ticTacBoard[i] = i;
    cout << endl;
}

void ticTacToeBoard ()
{
    for (int y = 0; y < 3; y++)
    {
        for (int x = 0; x < 3; x++)
            cout << ticTacBoard[3 * y + x] << " ";
        cout << endl;
    }
}

Upvotes: 1

Views: 86

Answers (5)

Blender
Blender

Reputation: 298056

Your i starts at 0, so your first value will be 0. Since the inequality i < 9 breaks when i = 9, i is actually never 9 (the loop exits before your code is actually run).

Try using <= instead of just < to account for i = 9:

for (int i = 1; i <= 9; i++)
{
    ticTacBoard[i - 1] = i;
}

Other than that, arrays are indexed starting from 0 in C++ (and virtually every other language), so the first element is array[0], second is array[1], etc.

You'll have to subtract 1 from your array index.

Upvotes: -1

John Humphreys
John Humphreys

Reputation: 39224

The loop:

for (int i = 1; i < 9; i++)
{
    ticTacBoard[i] = i;
}

will only do 1-8 since it will stop when i++ increases it to 9, so you're not initializing all 9 elements.

You should realistically do the same loop like this:

for (int i = 0; i < 9; i++)
{
    ticTacBoard[i] = (i + 1);
}

Upvotes: 2

Mark Byers
Mark Byers

Reputation: 837946

You have an off-by-one error. Arrays use zero-based indexing in C++. Your code does not assign a value to the zeroth element of the array.

Try this instead:

for (int i = 0; i < 9; i++)
{
    ticTacBoard[i] = i + 1;
}

Upvotes: 8

user
user

Reputation: 7333

Two suggestions:

  • Shouldn't you initialize ticTacBoard before accessing it with []? Make sure you give it enough memory for all of your slots! (I'm guessing you're doing tic tac toe, so you'll want 3x3 = 9 slots)
  • Indexing in C++ starts at 0. You want to do for (i=0; i<9; i++)

Hope this helps!

Upvotes: 1

shimofuri
shimofuri

Reputation: 691

Problem lies in:

ticTacBoard[i] = i;

Should be:

ticTacBoard[i-1] = i;

Upvotes: 1

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