3121. Count the Number of Special Characters II
Easy
You are given a string word. A letter c is called special if it appears both in lowercase and uppercase in word, and every lowercase occurrence of c appears before the first uppercase occurrence of c.
Return the number of special letters in word.
Example 1:
- Input: word = "aaAbcBC"
- Output: 3
-
Explanation: The special characters are
'a','b', and'c'.
Example 2:
Input: word = "abc"
Output: 0
Explanation: There are no special characters in word.
Example 3:
Input: "AbBCab"
Output: [0,1]
Explanation: There are no special characters in word.
Constraints:
1 <= word.length <= 2 * 105-
wordconsists of only lowercase and uppercase English letters.
Solution:
class Solution {
/**
* @param String $word
* @return Integer
*/
function numberOfSpecialChars($word) {
$first = array_fill(0, ord('z') + 1, 0);
$last = array_fill(0, ord('z') + 1, 0);
for ($i = 1; $i <= strlen($word); ++$i) {
$j = ord($word[$i - 1]);
if ($first[$j] == 0) {
$first[$j] = $i;
}
$last[$j] = $i;
}
$ans = 0;
for ($i = 0; $i < 26; ++$i) {
if ($last[ord('a') + $i] && $first[ord('A') + $i] && $last[ord('a') + $i] < $first[ord('A') + $i]) {
++$ans;
}
}
return $ans;
}
}
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