PermString.java

import java.util.Arrays;

class PermString{
    public static boolean checkInclusion(String s1, String s2) {

        if (s1.length() > s2.length() ) {
            return false;
        }

        int[] s1map = new int[26];
        int[] s2map = new int[26];

        for (int i = 0; i < s1.length(); i++) {
            s1map[s1.charAt(i) - 'a']++;
            s2map[s2.charAt(i) - 'a']++;
        }

        for (int i = 0; i < s2.length() - s1.length(); i++) {
            if (matches(s1map, s2map)) {
                return true;
            }
            s2map[s2.charAt(i + s1.length()) - 'a']++;
            s2map[s2.charAt(i) - 'a']--;
        }

        return matches(s1map, s2map);
    }

    public static void dsp(int[] s1map) {

        for (int i = 0; i < s1map.length; i++) {
            System.out.print(s1map[i] + " ");
        }
        System.out.println();
    }

    public static boolean matches(int[] s1map, int[] s2map) {

        for (int i = 0; i < s1map.length; i++) {
            if (s1map[i] != s2map[i]) {
                return false;
            }
        }

        return true;
    }

    public static void main(String[] args) {
        assert checkInclusion("ab", "eidbaooo") == true;

        assert checkInclusion("ab", "eidboaoo") == false;
    }
}