Another permutator

This is a solution to this problem. The problem statement:


write a program to display all possible permutations of a given input
string--if the string contains duplicate characters, you may have
multiple repeated results. Input should be of the form


permute string


and output should be a word per line.

This is my code:

#include 
#include 
#include 

std::vector permute(std::string s) {
    std::vector retval;
    if (s.length() > toPermute;
    } else {
        toPermute = argv[1];
    }

    std::vector result = permute(toPermute);

    std::cout << "Number of permutations: " << result.size() << std::endl;
    std::cout << std::string(24, '=') << std::endl;

    for (std::string permutation : result) {
        std::cout << permutation << std::endl;
    }
}

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Technically, the code doesn't meet the requirements: displaying number of permutations is not requested. You may add an option to display it as well, but a simple invocation permute string shall display only the permutations.

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Returns from permute: a non-void function with no return at the very end may raise some eyebrows.

Just extract return retval; out of if/else construct:

if (s.length() <= 1) {
    retval.push_back(s);
} else {
    ...
}
return retval;

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Algorithm has exponential time complexity. It is OK, because of the nature of task. It also requires exponential amount of memory, and it is not OK. You are not asked to keep all permutations, you just need to display them. And there is a solution with constant memory requirements.

StackExchange Code Review Q#58675, answer score: 4