<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>jj;
    void solve(string ip, string op){
        if(ip.length()==0){
            jj.push_back(op);
            return;
            }
        string op1=op;
        string op2=op;


        if(isdigit(ip[0])){
            op1.push_back(ip[0]);
            op2.push_back(ip[0]);
        }else{
            op1.push_back(ip[0]);
        if(isupper(ip[0]))op2.push_back(tolower(ip[0]));
        if(islower(ip[0]))op2.push_back(toupper(ip[0]));

        }
        
        ip.erase(ip.begin());
        solve(ip,op1);
        solve(ip,op2);
        return;
    }

    vector<string> letterCasePermutation(string s) {
        string ip=s;
        string op="";
        solve(ip,op);
        set<string>fi;

        for(auto let:jj){
            fi.insert(let);
        }
        vector<string>fil;
        for(auto l:fi){
            fil.push_back(l);
        }
        
        return fil;
    }
};
19300