1.1.java

/*
Implement an algorithm to determine if a string has all unique characters what if you can't use additional data structure
Date: 08/26/2014
*/
class solution{
  // Time complexity O(n^2), Space complexity O(1)
  public boolean check( String s ){
    boolean result = true;
    if( s.length() < 2 )// include string is empty
    result = true;
    
    int i, j;
    for( i = 0; i < s.length() - 1; i ++){
       for(j = i + 1; j < s.length(); j ++){
         if(s.charAt( i ) == s.charAt( j ) // charAt(int index) return a character of a string in position index. 
         result = false;
         break;
       }
      return true;
    }
    return result;
  }
}