String Remaining After Equal-Neighbor Erasure

### Problem Starting with lowercase string s, repeatedly erase an adjacent pair of equal letters until no such pair remains. Return the final string. The source guarantees this final string is unique, regardless of valid removal order. ```cpp class Solution { public: string removeDuplicates(string s); }; ``` ### Examples **Example 1:** ```text Input: s = "abccba" Output: "" Explanation: Erase cc, then bb, then aa. ``` **Example 2:** ```text Input: s = "aabccb" Output: "" Explanation: Erase aa and cc; the remaining bb also disappears. ``` ### Constraints - The input has between 1 and 100000 characters. - Every character is a lowercase English letter. ### Contract considerations Only adjacent equal pairs may be erased. An empty final string is valid. ```hint Read the boundary condition Can erasing a pair make two letters that were previously separated become adjacent? ``` ### Boundary reminders Only adjacent equal pairs may be erased. An empty final string is valid.