1.1

1.1.java

//Implement an algorithm to determine if a string has all unique characters. 
//What if you cannot use additional data structure
//first ask the string is Unicode string or ASCII string
// Unicode is a superset of ASCII, ASCII only defines 128 characters, which mappes 0-127
// but Unicode defines 2^21(maybe less than), and mappes to 0-2^21, 
// but the ASCII can be the same meaning in the Unicode
//the length of string is str.length()
//the length of array is array.length
//array[i], str.charAt(i). array=>[], string => ()
//time complexity is O(n)
public Solution{
	public boolean isUnique(String str){
		if(str == null || str.length() > 128 || str.length()< 0)
			return false;
		boolean check  = new boolean[256];
		for(i = 0;i<str.length();i++)
		{
			int val = str.charAt(i);
			if(check[val])
				return false;
			else check[val] = true;
		}
	}return true;
}

Why do you instantiate a boolean array with size of 256 instead of 128?
Note that ascii has 128 chars and ISO-8859-1(Latin 1) has 256 chars.

Is there a chance that str.length()<0?

Unicode case?