LetterCasePermutation.cpp

// Not necessary small case 
// digits also included 

#include<iostream>
#include<stack>
#include<vector>
#include<string>
using namespace std;
void solve(string ip,string op)
{
    if(ip.length()==0)
    {
        cout<<op<<endl;
        return;
    }
    if(isalpha(ip[0]))
    {
    string op1 = op;
    string op2 = op;
    op1.push_back(toupper(ip[0]));
    op2.push_back(tolower(ip[0]));
    ip.erase(ip.begin()+0);
    solve(ip,op1);
    solve(ip,op2);
    return;
}
else
{
   string op1 = op;
   op1.push_back(ip[0]);
   ip.erase(ip.begin()+0);
   solve(ip,op1);
return;
}

}
int  main() {
    string ip;
    cin>>ip;
    string op = " ";
    solve(ip,op);
    return 0;
}