<p>Given a string <code>s</code>, you&nbsp;can transform every letter individually to be lowercase or uppercase to create another string.</p>

<p>Return <em>a list of all possible strings we could create</em>. Return the output in <strong>any order</strong>.</p>

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

<pre>
<strong>Input:</strong> s = &quot;a1b2&quot;
<strong>Output:</strong> [&quot;a1b2&quot;,&quot;a1B2&quot;,&quot;A1b2&quot;,&quot;A1B2&quot;]
</pre>

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

<pre>
<strong>Input:</strong> s = &quot;3z4&quot;
<strong>Output:</strong> [&quot;3z4&quot;,&quot;3Z4&quot;]
</pre>

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

<ul>
	<li><code>1 &lt;= s.length &lt;= 12</code></li>
	<li><code>s</code> consists of lowercase English letters, uppercase English letters, and digits.</li>
</ul>

class Solution {
public:
    vector<string> letterCasePermutation(string s) {
        map<string , int> m;
        vector<string> ans;

        queue<string> q;

        q.push(s);

        while(q.size()!=0){
            string front = q.front();
            q.pop();

            if(m[front]==1){
                continue;
            }

            m[front]=1;
            ans.push_back(front);


            for(int i=0;i<front.size();i++){
                if(isalpha(front[i])){

                    string temp = front;

                    if(islower(temp[i])){
                        temp[i]=toupper(temp[i]);
                    } else {
                        temp[i]=tolower(temp[i]);
                    }

                    if(m[temp]!=1){
                        q.push(temp);
                    }
                }
            }

        }

        return ans;
    }
};
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