1209. Remove All Adjacent Duplicates in String II

문제)

1209. Remove All Adjacent Duplicates in String II

 

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.

솔루션1)

- 스택 자료구조 사용 (테트리스를 생각하면 됨)

class Solution:
    def removeDuplicates(self, s: str, k: int) -> str:
        # element : (char, count)
        stack = [[s[0], 1]]

        for c in s[1:]:
            if stack and stack[-1][0] == c:
                stack[-1][1] += 1
                if stack[-1][1] == k:
                    stack.pop()
            else:
                stack.append([c, 1])
    
        return ''.join([item[0] * item[1] for item in stack])