Reduce the string by removing K consecutive identical characters

Given a string str and an integer k, the task is to reduce the string by applying the following operation any number of times until it is no longer possible:

Choose a group of k consecutive identical characters and remove them from the string.

Finally, print the reduced string.

Examples:

Input: K = 2, str = "geeksforgeeks" 
Output: gksforgks 
Explanation: After removal of both occurrences of the substring "ee", the string reduces to "gksforgks".

Input: K = 3, str = "qddxxxd" 
Output: q 
Explanation: Removal of "xxx" modifies the string to "qddd". Again, removal of "ddd" modifies the string to "q". 

Approach: Using a Stack of Pairs - O(n) time and O(n) space

The approach uses a stack to track characters and their consecutive occurrences. As the string is processed, characters are pushed onto the stack with a count of consecutive occurrences. If a character repeats k times, it is skipped. After processing, the remaining characters in the stack are used to build the result string, which is then reversed to maintain the correct order.

gksforgks

Approach: Using a Single Stack - O(n) time and O(n) space

The approach uses a stack to remove consecutive characters that appear exactly k times. As we iterate through the string, we push each character onto the stack. If the top of the stack matches the current character, we increment a count. When the count reaches k, the characters are effectively removed. After processing the string, the remaining characters in the stack are popped and concatenated to form the final result.

gksforgks