## 1684. Count the Number of Consistent Strings

You are given a string allowed consisting of distinct characters and an array of strings words. A string is consistent if all characters in the string appear in the string allowed.

Return the number of consistent strings in the array words.

Example 1:

Output: 2
Explanation: Strings "aaab" and "baa" are consistent since they only contain characters 'a' and 'b'.

Example 2:

Input: allowed = "abc", words = ["a","b","c","ab","ac","bc","abc"]
Output: 7
Explanation: All strings are consistent.

Example 3:

Output: 4
Explanation: Strings "cc", "acd", "ac", and "d" are consistent.

Constraints:

• 1 <= words.length <= 104
• 1 <= allowed.length <= 26
• 1 <= words[i].length <= 10
• The characters in allowed are distinct.
• words[i] and allowed contain only lowercase English letters.

## Rust Solution

struct Solution;
use std::collections::HashSet;

impl Solution {
fn count_consistent_strings(allowed: String, words: Vec<String>) -> i32 {
let hs: HashSet<char> = allowed.chars().collect();
words
.into_iter()
.filter(|w| w.chars().all(|c| hs.contains(&c)))
.count() as i32
}
}

#[test]
fn test() {
let allowed = "ab".to_string();