CC 1.1

UniqueString.py

#1.1 Implement an algorithm to determine if a string has all unique characters. Whatif you cannot use additional data structures? 

test =[0 for i in range(255)]
re = 0
s= raw_input('Input:')

if s.strip() =='':
    print'This is empty string'
else:

    for i in range(0, len(s)):
        val = ord(s[i])
        if val in test:
	    print 'No, it is not unique'
	    break
        else:
            test[val] = val
            re += 1
if re == len(s):
    print 'Yes, it is unique'

A blank space is also a character, so you shouldn't use strip().
Using "val in test" will search the whole list, the time complexity of one search is O(n), and there will be n search operations. So you are implementing an algorithm with a time complexity of O(n^2)

Thanks a lot! I am not sure how to use index to search a list in python

There're two ways to do it. The first one is use a extra data structure, hashset(it's called set in python). It has a O(1) search time in average. The second is that, since the integer value of a character ranges from 0~255. So you can use an array of length 256, arr[i] indicating whether a char with integer value i is visited before.