Python - Remove K length Duplicates from String

To remove consecutive K-length duplicates from a string iterate through the string comparing each substring with the next and excluding duplicates. For example we are given a string s = "abcabcabcabc" we need to remove k length duplicate from the string so that the output should become "aaaabc" . We can use methods like Counter from collection , string replacement, list comprehension .

Using collections.Counter

Method counts substrings of length K and removes those that appear exactly K times.

from collections import Counter

s = "abcabcabcabc"
k = 3

# Count the occurrences of each substring of length K
sub_c = Counter(s[i:i+k] for i in range(len(s) - k + 1))

# Remove substrings that appear exactly K times
res = ''.join([s[i] for i in range(len(s) - k + 1) if sub_c[s[i:i+k]] != k] + [s[i] for i in range(len(s)-k+1, len(s))])

print(res)

aaaabc

Explanation:

• Counter() counts occurrences of all substrings of length K in the string s.
• New string is built by excluding substrings that appear exactly K times using a condition.

Using String Replacement

Method uses the replace() function to remove K-length duplicates explicitly.

s = "abcabcabcabc"
k = 3

# Loop to find and remove duplicates of length K
for i in range(len(s) - k + 1):
    if s[i:i+k] == s[i+k:i+2*k]:  # Check for consecutive K-length duplicates
        s = s[:i+k] + s[i+2*k:]

print(s)

abcabc

Explanation:

• Loop iterates through the string, checking if two consecutive substrings of length K are identical using s[i:i+K] == s[i+K:i+2*K].
• Consecutive duplicates are found string is updated by removing the second duplicate substring using slicing (s[:i+K] + s[i+2*K:])

Using Set and Sliding Window

This method uses a sliding window to keep track of substrings and removes duplicates by checking if the substring appears more than once.

s = "abcabcabcabc"
k = 3

res = []
seen = set()

# Traverse the string with a sliding window of size K
for i in range(len(s) - k + 1):
    sub = s[i:i+k]
    if sub not in seen:
        res.append(sub)
        seen.add(sub)


print(''.join(res))

abcbcacab

Explanation:

• Loop iterates through the string, checking if two consecutive substrings of length K are identical using s[i:i+K] == s[i+K:i+2*K].
• Consecutive duplicates are found string is updated by removing the second duplicate substring using slicing (s[:i+K] + s[i+2*K:])

Using List Comprehension

This method checks for duplicate substrings of length K and removes them by comparing substrings in a list comprehension.

s = "abcabcabcabc"
k = 3

# Using list comprehension to remove K-length duplicates
res = ''.join([s[i:i+k] for i in range(len(s) - k + 1) if s[i:i+k] not in s[i+k:i+2*k]])

print(res)

bcacababc

Explanation:

• List comprehension iterates over the string, extracting substrings of length K and checks if each substring is not repeated in the next consecutive substring of the same length.
• Substrings that are not duplicates are joined together using ''.join(), forming the final string without consecutive duplicates of length K.