3120. Count the Number of Special Characters I
Description
You are given a string word
. A letter is called special if it appears both in lowercase and uppercase in word
.
Return the number of special letters in word
.
Example 1:
Input: word = "aaAbcBC"
Output: 3
Explanation:
The special characters in word
are 'a'
, 'b'
, and 'c'
.
Example 2:
Input: word = "abc"
Output: 0
Explanation:
No character in word
appears in uppercase.
Example 3:
Input: word = "abBCab"
Output: 1
Explanation:
The only special character in word
is 'b'
.
Constraints:
1 <= word.length <= 50
word
consists of only lowercase and uppercase English letters.
Solutions
Solution 1: Hash Table or Array
We use a hash table or array $s$ to record the characters that appear in the string $word$. Then we traverse the 26 letters. If both the lowercase and uppercase letters appear in $s$, the count of special characters is incremented by one.
Finally, return the count of special characters.
The time complexity is $O(n + |\Sigma|)$, and the space complexity is $O(|\Sigma|)$. Where $n$ is the length of the string $word$, and $|\Sigma|$ is the size of the character set. In this problem, $|\Sigma| \leq 128$.
1 2 3 4 |
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 |
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 |
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1 2 3 4 5 6 7 8 9 10 11 12 |
|
1 2 3 4 5 6 7 8 9 10 11 12 13 |
|