Python - Remove K length Duplicates from String

Given a string s and an integer k, the task is to remove consecutive duplicate substrings of length k from the string. For Example:

Input: s = "abcababcabc", k = 3
Output: abcababc
Explanation: The repeated consecutive substring "abc" is reduced to a single occurrence, giving "abcababc".

Using String Slicing

This method uses string slicing to compare adjacent substrings of length k. It moves through the string from left to right and removes the second substring whenever two consecutive substrings are identical.

abcababc

Explanation:

• s[i:i+k] extracts the current substring of length k.
• s[i+k:i+2*k] extracts the next substring of length k.
• If both substrings are equal, the second one is removed using slicing.

Using a Stack-Like List

This method uses a list as a stack to store substrings of length k. It processes the string in fixed-size chunks and keeps only one copy when consecutive substrings are identical.

abcababc

Explanation:

• s[i:i+k] extracts the current substring of length k and s[i+k:i+2*k] extracts the next substring of length k.
• if s[i:i+k] == s[i+k:i+2*k] checks if consecutive substrings are identical.
• s = s[:i+k] + s[i+2*k:] removes the second substring if it’s a duplicate.
• i += 1 moves the pointer forward when no duplicate is found.

Using Regular Expressions

This method uses regular expressions with back-references to detect and remove consecutive duplicate substrings.

abcababc

Explanation:

• (.{k}) captures a substring of length k.
• (\1)+ matches one or more consecutive repetitions of that substring.
• re.sub() replaces repeated occurrences with a single copy.