Discover data structures and algorithms using Python. Gain insights into solving real-world problems and typical interview questions with detailed reviews, explanations, and hands-on coding exercises.

Data structures and algorithms are among the most fundamental concepts of Computer Science. Whether it’s real-world problems you’re trying to solve or the typical coding question asked in an interview, almost every problem requires you to demonstrate a deep understanding of data structures and algorithms. 

This course is a detailed review of some of the most common data structures and algorithms that you’ll see in interviews and your everyday work. With implementation details, thorough explanations, and hands-on coding exercises, you’ll quickly gain the confidence you need to solve any problem, no matter the situation.

Data Structures and Algorithms in Python

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: 

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 to a Python dictionary on **line 2**. Next, there is a `for` loop on **line 3** which iterates `input_str` character by character. In this `for` loop, the condition on **line 4** checks if `i`, i.e., the current character, is present in `d` or not. If it's not present in `d`, the execution jumps to **line 7** where it is then inserted into `d` as a key with `1` as its value. This is how we record the first instance of any character. However, if `d` is already present in `d`, it means that we encounter it on its second occurrence, which implies that it is not a unique character. Therefore, `False` is returned from the function in case `i` is present in `d`. 

If `False` is never returned from the function and the `for` loop terminates, `True` is returned on **line 8**.

I hope everything's been clear up until now!


# Solution 2 

Now, solution 2 is very concise and straightforward. In this solution, we make use of `set()`. Let's find out how by having a look at the implementation in Python. 

## Implementation

This lesson contains the solution review to determine whether a string contains all unique characters or not. 

Introduction

Stack

Singly Linked Lists

Circular Linked Lists

Doubly Linked Lists

Arrays

Binary Trees

Binary Search Trees

Binary Search

Recursion

String Processing

Solution Review: Is Unique

Solution 1

Implementation

Explanation