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Suppose we have two strings and I want to compare them character by character to check if any characters of string a and string b match or not?

An example:

$a = "Hello";  
$b = "world";

In the above 'o' exists in both strings , so the algorithm should echo exist.

Nico Haase
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Meiji
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3 Answers3

5

If you split the strings and remove the duplicates with array_unique, then array_intersect will give you characters that is in both strings. 

$a = "Hello";
$b = "world";

$matching = array_unique(array_intersect(str_split(strtolower($a)), str_split(strtolower($b))));
if(count($matching)>0) echo "matching characters: " . implode(", ", $matching); 
//matching characters: l, o

added strtolower as suggested by Ron.

Andreas
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  • I would also implement `strtolower` since `L` and `l` are the same in an alphabet. – Ron van der Heijden Aug 07 '18 at 10:34
  • if the purpose is only to print something when there is a match ,i think you could remove the step of array_unique which increase the time complexity.But if you want to know the matching characters too ,then this answer is great... – Elementary Aug 07 '18 at 10:46
  • @Elementary true. Another thing that makes the same result but faster is moving the array_unique to wrap the array_intersect means you only "unique" the intersected values which is less than 2x input strings. I think I will edit to do that instead – Andreas Aug 07 '18 at 11:01
  • i was thinking ... we can also write ` if($matching) echo "matching characters" .implode(", ",$matching);` to make code evaluation more fast... – Elementary Aug 07 '18 at 11:21
  • @Elementary I didn't think it would make that much difference. I actually thought without count would be slower due to type casting. But you are right, it's a lot faster actually. https://3v4l.org/Vfg6J Ok... something it not correct. I swapped order of them and the result is the opposite. https://3v4l.org/H0sjA – Andreas Aug 07 '18 at 11:34
  • test them separately show the difference @Andreas ...But online the result will always be a little biased.However good job. – Elementary Aug 07 '18 at 13:39
1

You could transform your strings using str_split() and get the matching characters with array_intersect():

$a = "Hello";
$b = "world";

$matching_chars = array_intersect(
    str_split($a),
    str_split($b)
);

if (empty($matching_chars)) {
    echo 'exist';
}

$matching_chars will be an array containing the letters l & o:

Array
(
    [2] => l
    [3] => l
    [4] => o
)
AymDev
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0
string1 = input()
string2 = input()

num_same = 0

for char1 in string1:
    for char2 in string2:
        if char1 == char2:
            num_same += 1

if num_same == 1:
    print(f'{num_same} character matches')
else:
    print(f'{num_same} characters match')
Henry Ecker
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user19568822
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  • Your answer could be improved with additional supporting information. Please [edit] to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers [in the help center](/help/how-to-answer). – Pedram marandi Jul 19 '22 at 23:53
  • Welcome to SO. The OPs question was about PHP, so this answer might not be helpful. Additionally, please don't post code-only answers but add a little textual explanation about how and why your approach works and what makes it different from the other answers given. You may also have a look at our ["How to write a good answer"](https://stackoverflow.com/help/how-to-answer) entry. – ahuemmer Jul 21 '22 at 06:34