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>> ZAMYLA CHAN: Let's have fun with 15.

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15 is the first game that
you get to implement.

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And it's interactive.

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Now, not to worry.

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You don't have to write the
whole thing yourself.

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>> Look at the distribution code.

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Because a lot of the game structure
is already set up for you.

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It accepts and parses a command line
argument from the user, and creates a

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board based on that input.

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>> It checks if the game is won, and exits
once the user's won the game.

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And to win the game, it gets
input from the user and

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calls the move function.

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So we're going to be implementing four
functions for the game of 15--

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init, draw, move, and won.

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>> First, let's tackle init.

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In init, for initialize, we represent
the board in a 2D integer array.

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And this is a global variable called
board with dimensions max and max, the

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maximum dimensions of the board.

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Now, the actual dimension of the board
is given by the user, represented in

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the integer d, which could
be less than max.

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But in C, you can't resize arrays.

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So you're stuck with that
maximum dimension.

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>> Your job in init is to populate
the values of the board

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with the correct values.

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Now, we've seen 1D arrays.

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But how do 2D arrays work?

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There's an index of the row,
0 index, as always, and

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then also of the column.

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>> And you'll fill your grid in in
descending values, just like this.

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Grid 0, 0, row 0, column 0, is 8.

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Grid 0, 1 is 7.

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This is for an example where
d, little d, is 3.

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Now, the board in 15 must also contain
a blank tile, if you've ever played

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with the physical game.

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>> But board is an integer array.

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So all values have to be integers.

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So it's up to you to decide an integer
value to represent a blank tile.

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>> To initialize your board, you can use
loop structures to contain the

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starting state of the board, where board
i, j represents the element at

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row i and column j.

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They start in descending order.

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And remember that if the number of tiles
is odd, then you're going to

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have to swap the location
of 2 and of 1.

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So there we have our initialized board.

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