remove-all-adjacent-duplicates-in-string-ii

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1209. Remove All Adjacent Duplicates in String II (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 lower case English letters.

Related Topics

[Stack] [String]

Hints

Hint 1

Use a stack to store the characters, when there are k same characters, delete them.

Hint 2

To make it more efficient, use a pair to store the value and the count of each character.