# 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.

```python
class Solution:
    def removeDuplicates(self, s: str, k: int) -> str:
        stack = []
        for char in list(s):
            if stack and stack[-1][0] == char:
                if stack[-1][1] == (k-1):
                    stack.pop()
                    # print('AFTER POP', stack)
                else:
                    stack[-1][1] += 1
            else:
                stack.append([char, 1])
            # print('ITER', stack)
        result = ""
        for char, count in stack:
            result += char*count
        return result
        
```