<p>You are given a string <code>s</code> that consists of lower case English letters and brackets.</p>

<p>Reverse the strings in each pair of matching parentheses, starting from the innermost one.</p>

<p>Your result should <strong>not</strong> contain any brackets.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;(abcd)&quot;
<strong>Output:</strong> &quot;dcba&quot;
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;(u(love)i)&quot;
<strong>Output:</strong> &quot;iloveu&quot;
<strong>Explanation:</strong> The substring &quot;love&quot; is reversed first, then the whole string is reversed.
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> s = &quot;(ed(et(oc))el)&quot;
<strong>Output:</strong> &quot;leetcode&quot;
<strong>Explanation:</strong> First, we reverse the substring &quot;oc&quot;, then &quot;etco&quot;, and finally, the whole string.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= s.length &lt;= 2000</code></li>
	<li><code>s</code> only contains lower case English characters and parentheses.</li>
	<li>It is guaranteed that all parentheses are balanced.</li>
</ul>

class Solution {
public:
    string reverseParentheses(string s) {
        int n=s.size();
        stack<string> st;
        for(int i=0; i<n; i++){
            if(s[i]=='(') st.push("(");
            else if(s[i]>=97 && s[i]<=122){
                string h;
                while(i<n && (s[i]>=97 && s[i]<=122)){
                    h.push_back(s[i]);
                    i++;
                }
                if(st.size()>0 && st.top()!="("){
                    string c=st.top();
                    st.pop();
                    h=c+h;
                    st.push(h);
                }
                else st.push(h);
                i=i-1;
            }
            else{
                string h=st.top();
                st.pop();
                if(h=="(") continue;
                reverse(h.begin(),h.end());
                st.pop();
                if(st.size()>0 && st.top()!="("){
                    h=st.top()+h;
                    st.pop();
                    st.push(h);
                }
                else st.push(h);
            }
        }
        while(st.size()>1){
            string f=st.top();
            st.pop();
            string l=st.top();
            st.pop();
            st.push(l+f);
        }
        return st.top();
    }
};
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