1128-remove-all-adjacent-duplicates-in-string.cpp

class Solution {
public:
    string removeDuplicates(string s) {
        stack<char> stk;
        int n = s.size();
        for (int i = 0; i < n; i++){
            if(stk.empty())
                stk.push(s[i]);
            else if(stk.top() == s[i])
                stk.pop();
            else
                stk.push(s[i]);        
        }
        string ans;
        while(!stk.empty()) {
            ans += stk.top();
            stk.pop();
        }
        reverse(ans.begin(), ans.end());
        return ans;
    }
};