Summer Coding Challenges

Print numbers 1–100. For multiples of 3 print "Fizz", multiples of 5 print "Buzz", both print "FizzBuzz".

Write a function that takes a string and returns it reversed. Do it without using Python's built-in slice shortcut.

Write a function that counts how many vowels (a, e, i, o, u) are in a given string. Make it case-insensitive.

Write a function that adds up all numbers in a list without using Python's built-in sum() function.

Find the largest number in a list without using Python's max() function or sorting.

Write a function that prints the full times table for a given number (1 to 12).

Write a function that returns True if a word or phrase is a palindrome (reads the same forwards and backwards). Ignore spaces, punctuation and case.

Encrypt a string by shifting each letter forward by n places in the alphabet. Wrap around from Z to A. Leave non-letters unchanged.

Count how many times each word appears in a string. Return the results as a dictionary sorted by frequency (most common first).

Write a function that converts a binary string (e.g. "1011") to its decimal equivalent WITHOUT using int(x, 2).

Write a function that returns True if a number is prime. Then use it to print all primes up to 100.

Implement a Stack class with push(), pop(), peek(), is_empty() and size() methods. Use a list internally but don't expose it directly.

Write a function that returns True if two strings are anagrams of each other (same letters, different order). Ignore spaces and case.

Write a recursive Fibonacci function. First write the naive version, then add memoisation to avoid recalculating the same values. Time both.

Implement binary search on a sorted list — WITHOUT using Python's bisect module. Return the index of the target, or -1 if not found.

Implement merge sort from scratch. Write a recursive function that splits a list in half, sorts each half, then merges them back together in order.

Evaluate a mathematical expression written in Reverse Polish Notation (postfix). Use a stack to process tokens left to right.

Given a start word and end word, find the shortest sequence of single-letter changes that gets from one to the other, where every intermediate step must be a real word. Use BFS.

Implement run-length encoding (RLE): compress a string by replacing consecutive repeated characters with the character and its count. Also write a decompressor.

Build a singly linked list from scratch with a Node class and LinkedList class. Implement: append, prepend, delete, search, and print_list.