class Solution {
    public boolean checkInclusion(String s1, String s2) {
        if(s1.length() > s2.length()) return false;
        
        int [] f1 = new int[26];
        int [] f2 = new int[26];
        
        for(int i=0; i<s1.length(); i++)
            f1[s1.charAt(i) - 'a']++;        
        
        for(int i=0; i<s2.length(); i++)
        {
            f2[s2.charAt(i)-'a']++;
            if(i >= s1.length())
                f2[s2.charAt(i-s1.length()) -'a']--;
            if(Arrays.equals(f1, f2)) return true;
        }
        return false;
    }
}