Coding solutions

Here are some coding solutions to common problems:

1. Reverse a string

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

2. Check if a number is prime

def is_prime(n):
    if n <= 1:
        return False
    for i in range(2, int(n ** 0.5) + 1):
        if n % i == 0:
            return False
    return True

3. Find the maximum value in a list

def max_value(lst):
    return max(lst)

4. Check if a string is a palindrome

def is_palindrome(s):
    return s == s[::-1]

5. Calculate the factorial of a number

def factorial(n):
    if n == 0:
        return 1
    else:
        return n * factorial(n-1)

6. Find the sum of all elements in a list

def sum_list(lst):
    return sum(lst)

7. Check if a number is even or odd

def is_even(n):
    return n % 2 == 0

8. Find the first duplicate in a list

def first_duplicate(lst):
    seen = set()
    for item in lst:
        if item in seen:
            return item
        seen.add(item)
    return None

9. Check if a string contains a specific substring

def contains_substring(s, sub):
    return sub in s

10. Find the longest common prefix in a list of strings

def longest_common_prefix(lst):
    if not lst:
        return ""
    prefix = lst[0]
    for s in lst[1:]:
        while not s.startswith(prefix):
            prefix = prefix[:-1]
    return prefix

11. Check if a number is a power of 2

def is_power_of_two(n):
    return n > 0 and (n & (n - 1)) == 0

12. Find the median of a list

def median(lst):
    lst.sort()
    n = len(lst)
    if n % 2 == 1:
        return lst[n//2]
    else:
        return (lst[n//2 - 1] + lst[n//2]) / 2

13. Check if a string is a valid email address

import re
def is_valid_email(s):
    pattern = r"^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$"
    return re.match(pattern, s) is not None

14. Find the first missing positive integer in a list

def first_missing_positive_integer(lst):
    lst = set(lst)
    i = 1
    while i in lst:
        i += 1
    return i

15. Check if a number is a perfect square

def is_perfect_square(n):
    return int(n ** 0.5) ** 2 == n

These are just a few examples of coding solutions to common problems. There are many more out there, and you can always find more by searching online or practicing coding challenges.

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Coding solutions