C# Coding Challenges

Challenge 1: Basic Data Manipulation

Problem:

Write a program to calculate the frequency of each character in a given string (case-insensitive) and display the results in alphabetical order. Ignore spaces and special characters.

Requirements:

The program should take a string as input from the user.
Count each letter's frequency.
Display the output in alphabetical order (e.g., A: 3, B: 1, ...).

Example Input:

"Hello, World!"

Expected Output:

D: 1
E: 1
H: 1
L: 3
O: 2
R: 1
W: 1

Challenge 2: Reverse Words in a Sentence

Objective:
Write a C# program that reverses the words in a sentence while maintaining the original word order and sentence structure.

Input:
"Hello World! How are you?"

Output:
"you? are How World! Hello"

Requirements:

The user will provide a sentence (could include punctuation, spaces, etc.).
Return the sentence with each word reversed but the order of the words maintained.

Considerations:

You should not reverse the letters in the words; only the order of the words should be reversed.
Handle punctuation and spaces properly (they should stay attached to the word they belong to).

Example Test Cases:

Input: "Coding is fun!"

Output: "fun! is Coding"

Challenge 3: Check for Palindromes in a Sentence

Problem:
Write a C# program that takes a sentence as input and identifies all the words that are palindromes. A palindrome is a word that reads the same backward as forward (e.g., "radar", "level").

Requirements:

Ignore case sensitivity (e.g., "Radar" should be treated as a palindrome).
Ignore punctuation and spaces in the input.
Identify and output all the palindromic words in the sentence.
If no palindromes exist, notify the user.
Avoid duplicate palindrome results in the output.

Example Input:
Enter a sentence: "Madam Arora teaches malayalam and a radar is nearby."

Expected Output:

Palindromes found: Madam, Arora, malayalam, radar

Challenge 4: Anagram Detector

Problem:
Write a C# program that takes two strings as input and checks if they are anagrams of each other. Definition of an Anagram: Two strings are anagrams if they contain the same characters in the same frequency, but possibly in a different order.

Requirements:

Ignore spaces and case differences while comparing the strings.
Check if both strings contain exactly the same characters with the same frequency.

Example Input:

String 1: "Listen"
String 2: "Silent"

Expected Output:

The strings are anagrams.

Challenge 5: Count Vowels and Consonants in a String

Problem:
Write a C# program that counts the number of vowels and consonants in a given string. Ignore spaces, punctuation, and other non-alphabetic characters. Your program should print the total count of vowels and consonants separately.

Input:
A sentence entered by the user.
Example Input: "Hello, world!"

Output:

Total Vowels: 3
Total Consonants: 7

Requirements:

Create a method to count vowels and consonants in the string.
Use a foreach loop to iterate through each character.
Make the program case-insensitive.
Output the results to the console.

Challenge 6: Number Pyramid

Problem:
Write a C# program that prints a number pyramid with a given number of rows. The pyramid should be symmetrical and made of numbers.

Input:
The user provides the number of rows for the pyramid.
Example Input: 5

Output:

Requirements:

Each row should have an increasing sequence of numbers followed by a decreasing sequence.
The pyramid should be properly aligned (use spaces to center the numbers).

Challenge 7: Find the Missing Number in an Array

Problem:
You are given an array of distinct numbers taken from a range. The array contains numbers from a to b, but one number is missing. Your task is to find the missing number in this range. The range can start from any number, not necessarily 1.

Approach:

We can use the sum formula for an arithmetic sequence to efficiently find the missing number. The sum of numbers from a to b is given by the formula:

Sum(a, b) = (b - a + 1) × (a + b) / 2

Steps:

Calculate the expected sum of the range from a to b using the formula.
Calculate the actual sum of the numbers in the array.
The missing number is the difference between the expected sum and the actual sum.

Example:

Given the array: [3, 4, 5, 7, 8]
Range: 3 to 8
Missing number: 6
1. Calculate the expected sum:
   Sum(3, 8) = (8 - 3 + 1) × (3 + 8) / 2 = 6 × 11 / 2 = 33
2. Calculate the actual sum of the array:
   3 + 4 + 5 + 7 + 8 = 27
3. The missing number:
   Missing = 33 - 27 = 6

Requirements:

Input: An array of distinct numbers and the range (a to b).
Output: The missing number in the array.

Challenge 8: Find and Display Missing Numbers in a Sequence

Problem:
You are given a sequence of integers that should form a continuous sequence without gaps. However, some numbers may be missing from the sequence. Your task is to identify and display all the missing numbers.

Requirements:

Input: A comma-separated list of integers (can be in any order).
Output: A list of missing numbers, or "No missing numbers" if none are missing.
Handle edge cases where no numbers are missing.
Efficiently identify missing numbers without brute force.

Steps:

Parse the input to extract integers from the list.
Find the minimum and maximum numbers in the sequence.
Generate the full range of numbers from the minimum to the maximum.
Compare the generated range with the input sequence to find missing numbers.
Output the missing numbers or print "No missing numbers" if the sequence is complete.

Example:

Input: 1, 2, 4, 5, 7, 9
Output: The missing numbers are: 3, 6, 8

Input: 1, 2, 3, 4, 5
Output: No missing numbers

Input: 18, 12, 13, 15, 16
Output: The missing numbers are: 11, 14

Challenge 9: Find the Most Frequent Character

Problem:
Write a program to find the most frequently occurring character in a given string. If there is a tie (two or more characters appear the same maximum number of times), return any one of them.

Requirements:

Input: A string entered by the user (e.g., "characteristics").
Output: The most frequent character in the string.
Ignore spaces (they shouldn't be counted).
Consider case sensitivity (e.g., 'A' and 'a' are different characters).

Steps:

Parse the string to count the occurrences of each character.
Ignore spaces when counting characters.
Check the frequency of each character and determine the one with the highest frequency.
If multiple characters have the same frequency, return any one of them.
Output the most frequent character.

Example:

Input: "characteristics"
Output: The most frequent character is: 'c'

Challenge 10: Multifaceted Puzzle - Character Analysis and Sequence Finder

Problem:
Write a program that analyzes a given string and performs the following:

1. Character Frequency Analysis:
Identify the top 3 most frequently occurring characters (case-insensitive). If two characters have the same frequency, prioritize lexicographically smaller characters (e.g., 'a' over 'b').

2. Longest Consecutive Sequence:
Find the longest consecutive sequence of any character (e.g., "aaabbcccaaa" has a sequence of "aaa" with a length of 3).

3. Generate a New String:
Construct a new string that contains:

The top 3 characters from step 1, each repeated by their frequency.
The longest sequence from step 2 appended to the end.

Requirements:

Input: A string entered by the user (e.g., "aaabbcccaaadddeefff").
Output: A string with:
- The top 3 most frequent characters.
- The longest consecutive sequence of any character.

Steps:

Parse the string and analyze the frequency of each character.
Identify the top 3 most frequent characters, resolving ties lexicographically.
Find the longest consecutive sequence of any character in the string.
Construct a new string based on the top 3 characters and the longest consecutive sequence.

Example:

Input: "aaabbcccaaadddeefff"
Output:
Top 3 characters:
a: 6
c: 3
f: 3
Longest consecutive sequence: aaa (length: 3)
Generated string: aaaaaacccfffaaa