Erase Equal Adjacent Runs of Size k

### Problem Repeatedly remove k adjacent equal letters from s, joining the two surrounding pieces after every removal. Return the final string when no removal remains. The source guarantees the final string is unique. ```cpp class Solution { public: string removeDuplicates(string s, int k); }; ``` ### Examples **Example 1:** ```text Input: s = "aabbbac", k = 3 Output: "c" Explanation: Removing bbb joins the a letters into aaa, which then disappears. ``` **Example 2:** ```text Input: s = "aaaa", k = 3 Output: "a" Explanation: One group of three disappears and one a remains. ``` ### Constraints - The input has 1 to 100000 lowercase English letters. - k is an integer from 2 through 10000. ### Contract considerations No choice of removal order needs to be returned; the final string is deterministic. ```hint Read the boundary condition Can removing a group create a new eligible group across the gap, and may the final result be empty? ``` ### Boundary reminders No choice of removal order needs to be returned; the final string is deterministic.