<p>Given a string <code>s</code> that contains parentheses and letters, remove the minimum number of invalid parentheses to make the input string valid.</p>

<p>Return <em>a list of <strong>unique strings</strong> that are valid with the minimum number of removals</em>. You may return the answer in <strong>any order</strong>.</p>

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

<pre>
<strong>Input:</strong> s = &quot;()())()&quot;
<strong>Output:</strong> [&quot;(())()&quot;,&quot;()()()&quot;]
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;(a)())()&quot;
<strong>Output:</strong> [&quot;(a())()&quot;,&quot;(a)()()&quot;]
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;)(&quot;
<strong>Output:</strong> [&quot;&quot;]
</pre>

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

<ul>
	<li><code>1 &lt;= s.length &lt;= 25</code></li>
	<li><code>s</code> consists of lowercase English letters and parentheses <code>&#39;(&#39;</code> and <code>&#39;)&#39;</code>.</li>
	<li>There will be at most <code>20</code> parentheses in <code>s</code>.</li>
</ul>

class Solution {
public:
    bool isStringValidParentheses(string s)
    {
        if(s.length() == 0) return true;
  
        int count = 0;
        for(char ch:s)
        {
           if(ch == '(')
            count++;
           else if(ch == ')')
            count--;

            if(count<0)
                return false;
        }
        return count == 0 ? true : false;        
    }

    vector<string> removeInvalidParentheses(string s) {
        
        set<string> setResult;
        vector<string> result;
        string str = "";
       // if(s.length()<2) return result;

        if(isStringValidParentheses(s))
        {
            result.push_back(s);
            return result;
        }

        queue<string> q;
        q.push(s);
        setResult.insert(s);
        bool found = false;
        while(!q.empty())
        {
            string curStr = q.front();
            // std::cout << "Cur Str : "<<curStr << endl;
            if(isStringValidParentheses(curStr))
            {
                result.push_back(curStr);

                // result.insert(curStr);
                // std::cout << "Found : "<<curStr << endl;
                found = true;
            }
            else if(found == false)
            {
                for(int i=0; i<curStr.length(); i++)
                {
                    if(curStr[i] == '(' || curStr[i] == ')')
                    {
                        string updatedStr = curStr;
                        updatedStr.erase(updatedStr.begin()+i);
                        if(setResult.find(updatedStr) == setResult.end())
                        {
                            q.push(updatedStr);
                            setResult.insert(updatedStr);
                        }
                    }
                }
            }

            q.pop();
        }

        // for(auto cur:setResult)
        // {
        //     result.push_back(cur);
        // }

        return result;
    }
};
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