3408 Count The Number Of Special Characters I

Count the Number of Special Characters I

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.

impl Solution {
    pub fn number_of_special_chars(word: String) -> i32 {
        use std::collections::HashSet;
        let s: HashSet<char> = word.chars().collect();
        let mut ans = 0;
        for c in 'a'..='z' {
            if s.contains(&c) && s.contains(&c.to_uppercase().next().unwrap()) {
                ans += 1;
            }
        }
        ans
    }
}