How to replace certain characters in a string and print each permutation?

[Adrian B]

Hi

I am looking to replace each "B" with "A" and each "D" with "C" in the string "BAD" but listing each permutation

i.e.

BAD
AAD
BAC
AAC

Hope this is clear as to what i am looking for.
I have not done any programming for many years and like php, so am trying to learn various functions and ways of going about solving problems. I am very rusty lol Please help. Much appreciated.
Regards
Adrian

[paulrajj]

Hi,

Check out the below code..

echo $str = "BAD"; echo "<br>";
$strlen = strlen($str);
for($i=0; $i<$strlen; $i++) {
    $ascii = ord($str[$i]);
    if($ascii != 65) {
        if($i == 1) {
            $str[$i] = chr($ascii-1);
        } else {
            $str[0] = chr(ord($str[0])-1);
        }
    } else {
        if($i == 1) {
            $str[0] = chr(ord($str[0])+1);
            $str[2] = chr(ord($str[2])-1);
        }
    }
    echo $str.'<br>';
}

[Adrian B]

mate thats spot on, thanks alot

now i just need to disect it and understand it lol

thanks again

Adrian B

[kovik]

Sounded like a homework assignment to me... You generally shouldn't give the code for trivial exercises like this one, since they are likely homework-related.

[Adrian B]

Was not a homework assignment at all. I am 35 and a drainage engineer. I did programming for homework many years ago when i was at college. Just fancy having ago at programming again in spare time. Like i said in my first post, i am a bit rusty.
FYI i am messing about with trying to make a word game in php that is similar to anagram solving etc.. thanks.

[kovik]

Oh. Okay then. Normally, people tell us what they are trying to do before asking such a vague question. My apologies.

[paulrajj]

Hi Adrian,

Have a look at this three functions in php to understand the snippet.
ord - Return ASCII value of character
chr - Return a specific character
strlen - Get string length

In a for loop using strlen function, I just converted each character of the string "BAD" to its ascii value(ord), then using the conditions i just rearranged the character positions, then converted it into its character using chr function and shown in a loop.

[kovik]

How about:

/**
 * Get all permuations of a string based on an array of translations
 *
 * @author Kovik :) http://koviko.net/
 * @param string $str
 * @param array $rules
 * @return array
 */
function get_all_permutations($str, array $rules) {
    $rules_power_set = array(array());
 
    foreach ($rules as $from => $to) {
        foreach ($rules_power_set as $current_set) {
            $rules_power_set[] = array_merge(array($from => $to), $current_set);
        }
    }
 
    $permutations = array();
 
    foreach ($rules_power_set as $rules) {
        $permutations[] = strtr($str, $rules);
    }
 
    return $permutations;
}

And use it like this:

$str = 'BAD';
$rules = array(
    'B' => 'A',
    'D' => 'C',
);
 
$permutations = get_all_permutations($str, $rules);
 
echo '<pre>' . print_r($permutations, true) . '</pre>';