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Asked: 2024-09-27T06:10:42+05:30 In:

How can I efficiently implement run-length encoding and decoding in Python?

I recently dove into the fascinating world of run-length encoding, and it’s been quite an eye-opener! For those who might not be familiar, run-length encoding is this neat way of compressing strings by summarizing consecutive repeated characters. For example, instead of writing “AAAABBBCCDAA”, you can just say “4A3B2C1D2A”. It’s a simple concept but can really save space when dealing with lots of repeated characters.

Now, I’ve been playing around with some examples, and I thought it might be fun to create a little challenge for everyone. Here’s what I’m thinking: How about we come up with a short program (or a snippet) that takes a string and returns its run-length encoded version? Bonus points if your solution is super concise—I always love seeing creative, short approaches!

I wrote this simple function in Python, but the result came out a bit longer than I wanted. I used a loop to count adjacent characters, then stored the counts and characters in a list. It worked, but it felt a bit bulky. I’d love to see how others approach this problem!

Let’s add a twist: how about we also include a feature to decode the run-length encoded string back to its original format? That just adds a new layer of complexity and makes it more interesting, right?

So here’s a couple of examples to get the creative juices flowing:

1. Input: “AAABBCCDA”
Output: “3A2B2C1D1A”

2. Input: “AABCCCCD”
Output: “2A1B4C1D”

And decoding should work like:

1. Input: “3A2B2C1D1A”
Output: “AAABBCCDA”

2. Input: “2A1B4C1D”
Output: “AABCCCCD”

I can’t wait to see how inventive everyone gets with their solutions! If you manage to keep it short and sweet, that would be amazing. Let’s see who can come up with the most efficient, elegant, or even the quirkiest solution! Happy encoding and decoding!

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    2 Answers

    1. Run-Length Encoding and Decoding Challenge!

      Here’s a simple Python solution to both encode and decode strings using run-length encoding!

      Encoding Function

      def encode_string(s):
    encoded = ""
    count = 1
    
    for i in range(1, len(s)):
        if s[i] == s[i - 1]:
            count += 1
        else:
            encoded += str(count) + s[i - 1]
            count = 1
    encoded += str(count) + s[-1]  # Add the last group
    return encoded

      Decoding Function

      def decode_string(encoded):
    decoded = ""
    num = ""
    
    for char in encoded:
        if char.isdigit():
            num += char
        else:
            decoded += char * int(num)  # Repeat current character num times
            num = ""  # Reset num for the next count
    return decoded

      Examples

      Let’s test it!

      # Encoding
print(encode_string("AAABBCCDA"))  # Output: "3A2B2C1D1A"
print(encode_string("AABCCCCD"))   # Output: "2A1B4C1D"

# Decoding
print(decode_string("3A2B2C1D1A"))  # Output: "AAABBCCDA"
print(decode_string("2A1B4C1D"))   # Output: "AABCCCCD"

      Feel free to tweak the code and have fun!

    2. Here’s a concise Python solution for both the run-length encoding and decoding tasks you’re interested in. The encoding function, run_length_encode, compresses the input string by counting consecutive characters and returning a compact representation. The decoding function, run_length_decode, reverses this process to get back the original string. Both functions emphasize brevity and clarity, demonstrating clean and efficient approaches to the problem.

      def run_length_encode(s):
    return ''.join(f'{len(list(g))}{k}' for k, g in groupby(s))

def run_length_decode(s):
    return ''.join(k * int(n) for n, k in zip(s[::2], s[1::2]))

# Example use:
print(run_length_encode("AAABBCCDA"))  # Output: "3A2B2C1D1A"
print(run_length_decode("3A2B2C1D1A"))  # Output: "AAABBCCDA"

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