PHP Program to check a string is a rotation of another string
Given the two strings we have to check if one string is a rotation of another string. Examples:
Input : $string1 = "WayToCrack",
$string2 = "CrackWayTo";
Output : Yes
Input : $string1 = "WillPower"
$string2 = "lliW";
Output : No.
The above problem can be easily solved in other languages by concatenating the two strings and then would check if the resultant concatenated string contains the string or not. But in PHP we will use an inbuilt function to solve the problem. The inbuilt functions used are:
1. strpos():
strpos() function generally accepts the two parameters first one to specify the string to be searched and the other one to find in the specified string.
In PHP solution strpos() will give the last position of string if found in the specified string. Below is the implementation of above approach.
<?php
function rotation_string($string1, $string2)
{
// if both strings are not same length then stop
if (strlen($string1) != strlen($string2))
echo "No";
// concatenate $string1 to itself, if both
// strings are of same length
if (strlen($string1) == strlen($string2))
$string1 = $string1.$string1;
if (strpos($string1, $string2) > 0)
echo "Yes";
else
echo "No";
}
// Driver code
$string1 = "WayToCrack";
$string2 = "CrackWayTo";
rotation_string($string1, $string2);
?>
Output
Yes
Using Substring Comparison
You can determine if one string is a rotation of another string by checking if one string is a substring of the other string concatenated twice.
Example:
<?php
function isRotation($string1, $string2) {
// Check if both strings are of the same length and not empty
if (strlen($string1) != strlen($string2)) {
return "No";
}
// Concatenate string1 with itself
$concatenated = $string1 . $string1;
// Check if string2 is a substring of the concatenated string
if (strpos($concatenated, $string2) !== false) {
return "Yes";
} else {
return "No";
}
}
// Example usage
$string1 = "WayToCrack";
$string2 = "CrackWayTo";
$result = isRotation($string1, $string2);
echo $result; // Output: Yes
?>
Output
Yes
Using str_contains() Function
The str_contains() function checks if a given substring is present within another string. By concatenating the first string with itself, you can check if the second string is a substring of the resulting string.
Example:
<?php
function isRotation($string1, $string2) {
// Check if lengths are different
if (strlen($string1) !== strlen($string2)) {
return "No";
}
// Concatenate $string1 with itself
$concatenated = $string1 . $string1;
// Check if $string2 is a substring of the concatenated string
if (str_contains($concatenated, $string2)) {
return "Yes";
} else {
return "No";
}
}
// Examples
$string1 = "WayToCrack";
$string2 = "CrackWayTo";
echo "Is '$string2' a rotation of '$string1'? " .
isRotation($string1, $string2) . PHP_EOL;
$string1 = "WillPower";
$string2 = "lliW";
echo "Is '$string2' a rotation of '$string1'? " .
isRotation($string1, $string2) . PHP_EOL;
?>
Output:
Is 'CrackWayTo' a rotation of 'WayToCrack'? Yes
Is 'lliW' a rotation of 'WillPower'? No
