205. Isomorphic Strings
Easy
Given two strings s and t, determine if they are isomorphic.
Two strings s and t are isomorphic if the characters in s can be replaced to get t.
All occurrences of a character must be replaced with another character while preserving the order of characters. No two characters may map to the same character, but a character may map to itself.
Example 1:
Input: s = “egg”, t = “add”
Output: true
Example 2:
Input: s = “foo”, t = “bar”
Output: false
Example 3:
Input: s = “paper”, t = “title”
Output: true
Constraints:
1 <= s.length <= 5 * 104
t.length == s.length
s and t consist of any valid ascii character.
Follow-up: Can you come up with an algorithm that is less than O(n2) time complexity?
Solution:
/**
* @param String $s
* @param String $t
* @return Boolean
*/
function isIsomorphic($s, $t) {
$last_seen_s = array_fill(0, 256, 0);
$last_seen_t = array_fill(0, 256, 0);
foreach (array_map(null, str_split($s), str_split($t)) as $index => [$char_s, $char_t]) {
$index += 1;
$ascii_s = ord($char_s);
$ascii_t = ord($char_t);
if ($last_seen_s[$ascii_s] != $last_seen_t[$ascii_t]) {
return false;
}
$last_seen_s[$ascii_s] = $last_seen_t[$ascii_t] = $index;
}
return true;
}
}
