Created
June 17, 2014 02:04
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#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' |
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.
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Thanks a lot! I am not sure how to use index to search a list in python