0438.找到字符串中所有字母异位词

impl Solution {
    pub fn find_anagrams(s: String, p: String) -> Vec<i32> {
        let mut ans = Vec::new();
        if p.len() > s.len() {
            return ans;
        }
        let (s, p) = (s.as_bytes(), p.as_bytes());
        let (mut s_cnt, mut p_cnt) = ([0; 26], [0; 26]);
        for (i, &c) in p.iter().enumerate() {
            s_cnt[(s[i] - b'a') as usize] += 1;
            p_cnt[(c - b'a') as usize] += 1;
        }
        if s_cnt == p_cnt {
            ans.push(0);
        }
        for i in p.len()..s.len() {
            let (pre_idx, idx) = ((s[i - p.len()] - b'a') as usize, (s[i] - b'a') as usize);
            s_cnt[idx] += 1;
            s_cnt[pre_idx] -= 1;
            if s_cnt == p_cnt {
                ans.push((i - p.len() + 1) as i32);
            }
        }
        ans
    }
}