Python Coding Exercise Algorithms

1. Reverse a String

        def reverse_string(s: str) -> str:
            return s[::-1]

        # Example usage
        print(reverse_string("hello"))  # Output: "olleh"
    

2. Find the Largest Number in a List

        def find_largest(nums: list) -> int:
            return max(nums)

        # Example usage
        print(find_largest([1, 2, 3, 4, 5]))  # Output: 5
    

3. Check if a Number is a Palindrome

        def is_palindrome(n: int) -> bool:
            return str(n) == str(n)[::-1]

        # Example usage
        print(is_palindrome(121))  # Output: True
        print(is_palindrome(123))  # Output: False
    

4. Fibonacci Sequence

        def fibonacci(n: int) -> list:
            fib_seq = [0, 1]
            for i in range(2, n):
                fib_seq.append(fib_seq[-1] + fib_seq[-2])
            return fib_seq[:n]

        # Example usage
        print(fibonacci(5))  # Output: [0, 1, 1, 2, 3]
    

5. Two Sum Problem

        def two_sum(nums: list, target: int) -> list:
            num_map = {}
            for i, num in enumerate(nums):
                complement = target - num
                if complement in num_map:
                    return [num_map[complement], i]
                num_map[num] = i

        # Example usage
        print(two_sum([2, 7, 11, 15], 9))  # Output: [0, 1]
    

6. Remove Duplicates from a List

        def remove_duplicates(nums: list) -> list:
            return list(set(nums))

        # Example usage
        print(remove_duplicates([1, 2, 2, 3, 4, 4, 5]))  # Output: [1, 2, 3, 4, 5]
    

7. Count the Number of Vowels in a String

        def count_vowels(s: str) -> int:
            vowels = 'aeiouAEIOU'
            return sum(1 for char in s if char in vowels)

        # Example usage
        print(count_vowels("hello world"))  # Output: 3
    

8. Merge Two Sorted Lists

        def merge_sorted_lists(list1: list, list2: list) -> list:
            merged = []
            i = j = 0
            while i < len(list1) and j < len(list2):
                if list1[i] < list2[j]:
                    merged.append(list1[i])
                    i += 1
                else:
                    merged.append(list2[j])
                    j += 1
            merged.extend(list1[i:])
            merged.extend(list2[j:])
            return merged

        # Example usage
        print(merge_sorted_lists([1, 3, 5], [2, 4, 6]))  # Output: [1, 2, 3, 4, 5, 6]
    

9. Find the First Non-Repeated Character in a String

        def first_non_repeated_char(s: str) -> str:
            counts = {}
            for char in s:
                counts[char] = counts.get(char, 0) + 1
            for char in s:
                if counts[char] == 1:
                    return char
            return None

        # Example usage
        print(first_non_repeated_char("swiss"))  # Output: "w"
    

10. Find the Intersection of Two Lists

        def list_intersection(list1: list, list2: list) -> list:
            return list(set(list1) & set(list2))

        # Example usage
        print(list_intersection([1, 2, 3, 4], [3, 4, 5, 6]))  # Output: [3, 4]