Mapping coordinates

[TomNL]

Hi,

I'm faced with a problem where I have a field of coordinates where every coordinate can be full (1) or empty (0).

Lets say the field looks like this:

1101011011010
0001011111010
0000010100110
0111010111101

This field is placed in an array and every end of a line is represented by a '2'
so, the array for the field below looks like (1,1,0,1,0,1,1,0,1,1,0,1,0,2,0,0,0,1,0 and so on)

I have an array that I must place in an empty spot in this field and the array cannot be broken in to pieces. This array always only consists of '1'-s. Lets say I have the following array that I want to place in the field.

'1,1,1,1,1'

It's obvious that there is one place in which I can put this string, third row first to fith position.

My question is how do I get PHP to find this empty spot in the field and place the string into this field.

And to make it even more challenging;
The piece i have to place into the field can also consist of multiple lines, like this

1111
1111

in an array it would look like (1,1,1,1,2,1,1,1,1) 2 represents a new line.

Would have to fit in a field (array) like:

111111111111
110000111111
110000111111
111111111111

I have been breaking my head over this, can someone please help me out or at least point me in the right direction?

[paulnaj]

One way would be to use regular expressions. It would mean using strings rather than array, but that's easy.

Your original field ...

1101011011010
0001011111010
0000010100110
0111010111101

... could be represented as ...

1101011011010200010111110102000001010011020111010111101

... using your 2's as end-of-lines.

<?php

$field = "1101011011010200010111110102000001010011020111010111101";

$item = '11111';


$field = preg_replace('/0{'.strlen($item).'}/', $item, $field);

?>

See how that fits into your scheme.

The 'multiple' issue should be solvable in a similar manner.
Paul 🙂

[trexx]

do you have to store all that in a string? if the answer is no i would recommend a different approach.

first: use a two dimensional array (array of arrays).

that would loke like this:

$coords = array($coords = array(
    array(1,1,0,1,0,1,1,0,1,1,0,1,0),
    array(0,0,0,1,0,1,1,1,1,1,0,1,0),
    ...
);

if you want to have an "empty slot" use a "null" instead of 0 or 1.

$coords = array($coords = array(
    array(1,1,0,1,0,1,1,0,1,1,null,1,0),
    array(0,0,0,1,0,1,1,1,1,1,0,1,0),
    ...
);

the next requirement of having multiple lines of 1111 in that field is easy:

$coords = array($coords = array(
    array(1,1,0,1,0,1,1,0,1,1,array(
                                array(1,1,1), 
                                array(1,1,1)),1,0),
    array(0,0,0,1,0,1,1,1,1,1,0,1,0),
    ...
);

if you need a string representation, use the serialize function of php after you have manipulated the data in the array. if you need a special string representation, write your own serialize-function. it's much easier AND faster to work with arrays, than to work with strings and regexp.

[paulnaj]

Hi trexx,

Might be faster, but you haven't suggested a way of navigating through your array of arrays to do the replacement.

Paul 🙂

BTW: A string is just an array of characters!

[trexx]

ehm... forget about my last post... :-)

thinking

[trexx]

okay... finished thinking =)

<?php
function printArray($data) {
    $dataY = count($data);
    $dataX = count($data[0]);

for ($y=0; $y<$dataY; $y++) {
    for ($x=0; $x<$dataX; $x++) {
        echo $data[$y][$x] . ' ';
    }
    echo "<br>\n";
}
}

function findHole($data, $holeY, $holeX) {
    $dataY = count($data);
    $dataX = count($data[0]);

$copyData = $data;  # we copy the values so we don't have
                    # to loop through the array twice

for ($y=0; $y<$dataY; $y++) {
    for ($x=0; $x<$dataX; $x++) {
        if ($copyData[$y][$x] == 0) {
            # we check if there is space for the array we want to fill in 
            for ($fy=0; $fy<$holeY; $fy++) {
                for ($fx=0; $fx<$holeX; $fx++) {
                    if ($copyData[$y + $fy][$x + $fx] === 1 || ($y + $fy) > $dataY || ($x + $fx) > $dataX) {
                        # there wasn't enough space, so we copy back
                        # the original array
                        $copyData = $data;
                        break 2;
                    } else {
                        # replace here... 
                        $copyData[$y + $fy][$x + $fx] = 2;
                    }
                }
            }
        }
    }    
}
return $copyData;
}

$data = array(
    array(1,1,1,1,1,1,1),
    array(1,1,0,0,0,1,1),
    array(1,1,0,0,0,1,1),
    array(1,1,1,1,1,1,1)
);


$data = findHole($data, 2, 3);
printArray($data);
?>

to the code: fill in your values in the $data array. then call the findHole() function. argument 2 and 3 are the size of the hole it has to find. When it finds a hole, it sets all the values in that hole to 2 (you may change that).

btw: sure, a string is an array of chars. but if you use regexp you start a whole regexp-engine, that parses your regexp, processes rules and finally really does something with your string - it does quite a bite more than just accessing the string directly. anyway... probably performance is not so important here but it's alyways fun being a smart ass 😃

ps: sorry, but i haven't read the problem properly the first time. so forget about the null values and array in array in array 🙂