Smallest Sub String

import java.util.*;
public class SmallSubString {
    static final int MAX_CHARS_COUNT = 256;

    static int maxDistChar(String str, int n)
    {
        int count[] = new int[MAX_CHARS_COUNT];
        int max_distinct = 0;
        for (int i = 0; i < n; i++) {
            count[str.charAt(i)]++;
            if (count[str.charAt(i)] == 1)
                max_distinct++;
        }
        return max_distinct;
    }

    static int smallestSubString(String str)
    {
        int n = str.length();
        int unique = maxDistChar(str, n);
        int res = Integer.MAX_VALUE;
        Map<Character, Integer> mp = new HashMap<Character, Integer>();
                 

        int j = 0;
        for (int i = 0; i < str.length(); i++) {
            char c = str.charAt(i);
            if (mp.containsKey(c))
                mp.put(c, mp.get(c) + 1);
            else
                mp.put(c, 1);
            while (mp.size() == unique
                    && mp.get(str.charAt(j)) > 1) {
                mp.put(str.charAt(j),
                        (mp.get(str.charAt(j)) - 1));
                j++;
            }
            if (mp.size() == unique)
                res = Math.min(i - j + 1, res);
        }
        return res;
    }

    static public void main(String[] args)
    {
        String str = "AABBBCBB";

        int len = smallestSubString(str);
        System.out.println(
                " The length of the smallest substring characters "+ len);
    }
}