Problem:
Score : 200 points

Problem Statement

You are given a string S of length N consisting of lowercase English letters.
We will cut this string at one position into two strings X and Y.
Here, we would like to maximize the number of different letters contained in both X and Y.
Find the largest possible number of different letters contained in both X and Y when we cut the string at the optimal position.

Constraints

2 \leq N \leq 100

|S| = N

S consists of lowercase English letters.

Input

Input is given from Standard Input in the following format:

N
S

Output

Print the largest possible number of different letters contained in both X and Y.

Sample Input 1

6
aabbca

Sample Output 1

2

If we cut the string between the third and fourth letters into X = aab and Y = bca, the letters contained in both X and Y are a and b.
There will never be three or more different letters contained in both X and Y, so the answer is 2.

Sample Input 2

10
aaaaaaaaaa

Sample Output 2

1

However we divide S, only a will be contained in both X and Y.

Sample Input 3

45
tgxgdqkyjzhyputjjtllptdfxocrylqfqjynmfbfucbir

Sample Output 3

9

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)


import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
	// write your code here
        Scanner scanner=new Scanner(System.in);
        final int N=scanner.nextInt();
        final String string=scanner.next();

        String alphabet="abcdefghijklmnopqrstuvwxyz";
        String[] strings=string.split("");
        int max=Integer.MIN_VALUE;
        for(int i=1;i<N;i++){
            boolean[] booleans1=new boolean[alphabet.length()];
            boolean[] booleans2=new boolean[alphabet.length()];
            for(int j=0;j<N;j++){
                if(j<i){
                    booleans1[alphabet.indexOf(strings[j])]=true;
                }else{
                    booleans2[alphabet.indexOf(strings[j])]=true;
                }
            }
            int subMax=0;
            for(int j=0;j<booleans1.length;j++){
                if(booleans1[j]&&booleans2[j]) subMax++;
            }
            if(max<subMax) max=subMax;
        }
        System.out.println(max);
    }
}