Level 1: Beginner

• Find the maximum number in a list without using `max()` function.
• Sort a list in ascending order without using the `sort()` function
• Reverse a string without using the `reversed()` function
• Count the number of vowels in a given string
• Check if a number is a palindrome
• Print the Fibonacci series up to `n` terms
• Find the sum of all numbers in a list without using `sum()` function

Level 2: Intermediate

• Find the second largest number in a list without using `max()` or `sorted()`
• Check if two strings are anagrams (e.g., "listen" and "silent")
• Remove all duplicate elements from a list without using `set()`
• Implement a function to find the factorial of a number using recursion
• Write a function to flatten a nested list
• Transpose a matrix represented as a list of lists without using built-in functions
• Write a function to check if a string is a valid rotation of another string

Level 3: Advanced

• Write a program to find the longest increasing subsequence in an array
• Implement a function to find the GCD of two numbers without using built-in libraries
• Generate all permutations of a string without using built-in libraries
• Write a program to implement matrix multiplication without using libraries
• Find the smallest positive integer missing from an unsorted array
• Implement your own version of the `map()` function
• Write a function to solve the "N-Queens" problem for a given board size `N`
• Write a function to solve n-size Spiral Matrix