letter_permutations.cpp

#include <iostream>
#include <map>
#include <string>
using namespace std;

map<char, char> alternatives;

void traverse(string prefix, string rest)
{
    if (rest.empty()) {
        cout << prefix << endl;
        return;
    }
    
    char first = rest[0];
    string end = rest.substr(1);
    
    traverse(prefix + first, end);
    if (alternatives.find(first) != alternatives.end()) {
        traverse(prefix + alternatives[first], end);
    }
}

int main(int argc, char const *argv[])
{
    alternatives['s'] = '$';
    alternatives['t'] = '+';
    alternatives['l'] = '|';
    alternatives['o'] = '0';
    alternatives['e'] = '3';
    alternatives['a'] = '@';
    alternatives['v'] = '^';
    
    traverse(string(""), string("bonoboape"));
    return 0;
}