LeetCode 1209 Remove All Adjacent Duplicates In String - Medium

1209. Remove All Adjacent Duplicates In String — Medium

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Problem

1209. Remove All Adjacent Duplicates in String II -- Medium

Given a string s, 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 <= 10^5 2 <= k <= 10^4 s only contains lower case English letters.

Solution

class Solution:
    def removeDuplicates(self, s: str, k: int) -> str:
        stack = []
        for letter in s:
            if stack and stack[-1][0] == letter:
                if stack[-1][1] == k - 1:
                    stack.pop()
                else:
                    stack[-1][1] += 1
            else:
                stack.append([letter, 1])   
        res = []
        for elem in stack:
            res.append(elem[0] * elem[1])
        return ''.join(res)