Remove all adjacent duplicates in string ii

class Solution:
    def removeDuplicates(self, s: str, k: int) -> str:
        stack = []
        for i in range(len(s)):
            char = s[i]
            if stack and stack[-1][0] == char:
                stack.append((char, stack[-1][1] + 1))
            else:
                stack.append((char, 1))

            if stack and stack[-1][1] == k:
                for j in range(k):
                    stack.pop()

        return "".join([i[0] for i in stack])

Remove All Adjacent Duplicates in String II

Difficulty: Medium

You are given a string s and an integer k, a k duplicate removal consists of choosing k adjacent and equal letters from s and removing them, causing the left and the right side of the deleted substring to concatenate together.

We repeatedly make k duplicate removals on s until we no longer can.

Return the final string after all such duplicate removals have been made. It is guaranteed that the answer is unique.

 

Example 1:

Input: s = "abcd", k = 2
Output: "abcd"
Explanation: There's nothing to delete.

Example 2:

Input: s = "deeedbbcccbdaa", k = 3
Output: "aa"
Explanation: 
First delete "eee" and "ccc", get "ddbbbdaa"
Then delete "bbb", get "dddaa"
Finally delete "ddd", get "aa"

Example 3:

Input: s = "pbbcggttciiippooaais", k = 2
Output: "ps"

 

Constraints:

  • 1 <= s.length <= 105
  • 2 <= k <= 104
  • s only contains lowercase English letters.