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Data Structures and Algorithms in Python

Solution Review: Is Unique

Explore different approaches to check if a string has all unique characters in Python. Understand implementations using dictionaries, sets, and character removal, along with their efficiency considerations.

We'll cover the following...

In this lesson, we will consider how to determine if a string has all unique characters. One approach to this problem may be to use an additional data structure, like a hash table. We will also consider how one may solve this problem without the use of such a data structure.

So, we’ll present a number of solutions to the problem posed in the previous challenge and give a rough time and space complexity analysis of each approach.

Let’s get started!

Solution 1

Now let’s discuss the actual implementation. Solution 1 uses a Python dictionary to solve the problem in linear time complexity, but because of the additional data structure, the space complexity is also linear.

Implementation

Below is the implementation of Solution 1 in Python:

Python 3.5
def is_unique_1(input_str):
    d = dict()
    for i in input_str:
        if i in d:
            return False
        else:
            d[i] = 1
    return True

Explanation

d is initialized ...