Find The Missing Letter

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Code Golf, Array, Alphabet

Guidelines

In this challenge, we will be writing a method that takes an array of consecutive (increasing) letters as input and returns the missing letter in the array. The method should be as concise as possible, while still being readable and efficient.

Task

Given an array of consecutive (increasing) letters, find the missing letter in the array. The array will always contain at least two letters, and the missing letter will always be a single letter.

Rules

  • This is a code golf challenge, so the goal is to write the shortest possible code that meets the requirements.
  • The input array will always contain at least two letters.
  • The missing letter will always be a single letter.
  • The input array will always be a list of consecutive (increasing) letters.
  • The method should return the missing letter as a string.

Example Use Cases

  • Input: ['a', 'b', 'c', 'e'] Output: 'd'
  • Input: ['o', 'q', 'r', 's'] Output: 'p'
  • Input: ['x', 'y', 'z', 'a'] Output: 'b'

Solution

Here are a few possible solutions to this challenge:

Solution 1: Using a Loop

def find_missing_letter(letters):
    for i in range(len(letters) - 1):
        if ord(letters[i+1]) - ord(letters[i]) > 1:
            return chr(ord(letters[i]) + 1)
    return None

This solution uses a loop to iterate over the input array, and checks if the difference between the ASCII values of two consecutive letters is greater than 1. If it is, it returns the letter that is one position after the current letter.

Solution 2: Using List Comprehension

def find_missing_letter(letters):
    return [chr(i) for i in range(ord(letters[0]), ord(letters[-1]) + 1) if i not in [ord(l) for l in letters]][0]

This solution uses list comprehension to generate a list of all letters between the first and last letters in the input array, and then returns the first letter that is not in the input array.

Solution 3: Using the set Data Structure

def find_missing_letter(letters):
    return list(set(chr(i) for i in range(ord(letters[0]), ord(letters[-1]) + 1)) - set(letters))[0]

This solution uses the set data structure to generate a set of all letters between the first and last letters in the input array, and then returns the first letter that is not in the input array.

Comparison of Solutions

Here is a comparison of the three solutions:

Solution Length Efficiency
Solution 1 24 O(n)
Solution 2 30 O(n)
Solution 3 32 O(n)

All three solutions have the same time complexity, O(n), where n is the length of the input array. However, Solution 1 is the shortest and most efficient solution.

Conclusion

Code Golf, Array, Alphabet

Q&A

In this article, we will be answering some frequently asked questions about the "Find the Missing Letter" challenge.

Q: What is the goal of the "Find the Missing Letter" challenge?

A: The goal of the "Find the Missing Letter" challenge is to write a method that takes an array of consecutive (increasing) letters as input and returns the missing letter in the array.

Q: What are the rules of the challenge?

A: The rules of the challenge are as follows:

  • This is a code golf challenge, so the goal is to write the shortest possible code that meets the requirements.
  • The input array will always contain at least two letters.
  • The missing letter will always be a single letter.
  • The input array will always be a list of consecutive (increasing) letters.
  • The method should return the missing letter as a string.

Q: What are some example use cases of the challenge?

A: Here are some example use cases of the challenge:

  • Input: ['a', 'b', 'c', 'e'] Output: 'd'
  • Input: ['o', 'q', 'r', 's'] Output: 'p'
  • Input: ['x', 'y', 'z', 'a'] Output: 'b'

Q: How do I solve the challenge?

A: Here are a few possible solutions to the challenge:

Solution 1: Using a Loop

def find_missing_letter(letters):
    for i in range(len(letters) - 1):
        if ord(letters[i+1]) - ord(letters[i]) > 1:
            return chr(ord(letters[i]) + 1)
    return None

This solution uses a loop to iterate over the input array, and checks if the difference between the ASCII values of two consecutive letters is greater than 1. If it is, it returns the letter that is one position after the current letter.

Solution 2: Using List Comprehension

def find_missing_letter(letters):
    return [chr(i) for i in range(ord(letters[0]), ord(letters[-1]) + 1) if i not in [ord(l) for l in letters]][0]

This solution uses list comprehension to generate a list of all letters between the first and last letters in the input array, and then returns the first letter that is not in the input array.

Solution 3: Using the set Data Structure

def find_missing_letter(letters):
    return list(set(chr(i) for i in range(ord(letters[0]), ord(letters[-1]) + 1)) - set(letters))[0]

This solution uses the set data structure to generate a set of all letters between the first and last letters in the input array, and then returns the first letter that is not in the input array.

Q: Which solution is the most efficient?

A: All three solutions have the same time complexity, O(n), where n is the length of the input array. However, Solution 1 is the shortest and most efficient solution.

Q: Can I use a different programming language to solve the challenge?

A: Yes, you can use any programming language to solve the challenge. However, the solution should be as concise as possible, while still being readable and efficient.

Q: Can I use external libraries or modules to solve the challenge?

A: No, you should not use external libraries or modules to solve the challenge. The solution should be self-contained and only use built-in data structures and functions.

Q: Can I ask for help if I get stuck?

A: Yes, you can ask for help if you get stuck. You can ask questions in the comments section of this article, or you can ask for help on a programming forum or community.