# Python 101: Solving 3 Essential Programming Challenges Step-by-Step

In this tutorial, we’ll go through solving three programming challenges using Python. We’ll cover:

- Reversing a string
- Finding the first non-repeated character
- Calculating the Fibonacci sequence

Let’s get started!

# 1. Reversing a string

Challenge: Write a function to reverse a given string.

`def reverse_string(s: str) -> str:`

return s[::-1]

# Test the function

input_string = "PythonRocks"

result = reverse_string(input_string)

print(f"Reversed string: {result}")

In this solution, we use Python’s slicing syntax to reverse the string. `s[::-1]`

means we start from the beginning to the end of the string, but with a step of -1, effectively reversing it.

# 2. Finding the first non-repeated character

Challenge: Write a function to find the first non-repeated character in a string.

`def first_non_repeated_char(s: str) -> str:`

char_count = {}

for char in s:

if char in char_count:

char_count[char] += 1

else:

char_count[char] = 1

for char in s:

if char_count[char] == 1:

return char

return None

# Test the function

input_string = "programming"

result = first_non_repeated_char(input_string)

print(f"First non-repeated character: {result}")

Here, we create a dictionary called `char_count`

to store the count of each character in the string. We then loop through the string to populate the dictionary. Finally, we loop through the string again and return the first character with a count of 1. If no such character is found, the function returns `None`

.

# 3. Calculating the Fibonacci sequence

Challenge: Write a function to calculate the first n numbers of the Fibonacci sequence.

`def fibonacci(n: int) -> list:`

if n <= 0:

return []

if n == 1:

return [0]

if n == 2:

return [0, 1]

sequence = [0, 1]

for i in range(2, n):

next_num = sequence[i - 1] + sequence[i - 2]

sequence.append(next_num)

return sequence

# Test the function

n = 10

result = fibonacci(n)

print(f"First {n} numbers of the Fibonacci sequence: {result}")

In this solution, we first handle the base cases for when `n`

is 0, 1, or 2. Then, we initialize the sequence with the first two Fibonacci numbers (0 and 1) and use a loop to calculate the rest of the sequence. We append each new number to the list and return the entire sequence.

These are just a few examples of programming challenges that can be solved using Python. Practice solving various challenges to improve your problem-solving skills and familiarity with the language.