gistfile1.java

import java.util.*;

public class UniqueChar {

    public static void main( String[] args ) {
		String[] strArray = { "abcdef", "dssfagagalglag" };
		for ( String str : strArray )
			System.out.println( isUniqueChar1( str ) );
		for ( String str : strArray )
			System.out.println( isUniqueChar2( str ) );
		for ( String str : strArray )
			System.out.println( isUniqueChar3( str ) );
	}
	//bitmap method
	public static boolean isUniqueChar1( String str ) {
		boolean [] set = new boolean[256];
		for ( int i = 0; i < 256; i++ )
			set[i] = false;
		int len = str.length();
		for ( int j = 0; j < len; j++ ) {
			int val = str.charAt( j );
			if ( set[val] == false )
				set[val] = true;
			else return false;
		}
		return true;

	}

	//hash table method
	public static boolean isUniqueChar2( String str ) {
		Map<Integer, Character> charMap = new HashMap<Integer, Character>();
		for ( int i = 0; i < str.length(); i++ ) {
			char val = str.charAt( i );
			int key = val;
			if ( ( charMap.containsKey( key ) ) == true )
				return false;
			else charMap.put( key, val );

		}
		return true;
	}

	//quicksort
	public static boolean isUniqueChar3( String str ) {
		char [] data = str.toCharArray();
		Arrays.sort( data );

		for ( int i = 0, arrlen = data.length; i < arrlen - 1; i++ ) {
			if ( data[i] == data[i + 1] )
				return false;
		}
		return true;
	}


}