public class DayCode {    public static void main(String[] args) {        String s1 = "ab", s2 = "eidbaooo";        boolean ans = new DayCode().checkInclusion(s1, s2);        System.out.println("ans is " + ans);    }
    /**     * https://leetcode-cn.com/problems/permutation-in-string/     * @param s1     * @param s2     * @return     */    public boolean checkInclusion(String s1, String s2) {        int n = s1.length();        int m = s2.length();        if (n > m) {            return false;        }        int[] cnt1 = new int[26];        int[] cnt2 = new int[26];        for (int i = 0; i < n; ++i) {            ++cnt1[s1.charAt(i) - 'a'];            ++cnt2[s2.charAt(i) - 'a'];        }        if (Arrays.equals(cnt1, cnt2)) {            return true;        }        for (int i = n; i < m; ++i) {            ++cnt2[s2.charAt(i) - 'a'];            --cnt2[s2.charAt(i - n) - 'a'];            if (Arrays.equals(cnt1, cnt2)) {                return true;            }        }        return false;    }}