LeetCode/rs/determine-if-two-strings-are-close.rs

use std::convert::TryFrom;

impl Solution {
    fn freqs(word: &str) -> Vec<usize> {
        let mut f = vec![0; 26];

        let zero = u8::try_from('a').unwrap();
        for c in word.chars().filter_map(|c| match u8::try_from(c) {
            Ok(val) => Some(val),
            _ => None,
        }) {
            f[(c - zero) as usize] += 1;
        }

        f
    }

    fn mask(f: &[usize]) -> i32 {
        let mut m = 0;

        for c in f {
            m = (m << 1) | if *c > 0 { 1 } else { 0 };
        }

        m
    }

    pub fn close_strings(word1: String, word2: String) -> bool {
        let mut f1 = Solution::freqs(&word1);
        let m1 = Solution::mask(&f1);
        f1.sort();

        let mut f2 = Solution::freqs(&word2);
        let m2 = Solution::mask(&f2);
        f2.sort();

        m1 == m2 && f1 == f2
    }
}