Split command line argument into arguments/a vector using C++ - c++

Question

I have a C++ project that was previously receiving multiple command line arguments with code like so:
int main(int argc, char *argv[]) {
for (int i = 1; i < 4; i = i + 1) {
// do some stuff with argv[i]
int in_arg = m[argv[i]];
}
return 0
}
Using this code, an example command line argument might be:
C:\MyFolder\MyExecutable.exe 4 0 1
However, due to plugging this code into a wider project my command line will now have to look like this instead:
C:\MyFolder\MyExecutable.exe 401
How can I split the argument 401 into a vector or similar that is functionally the same as having three input arguments like 4 0 1 so that my line:
int in_arg = argv[i];
...could be repointed to something like:
int in_arg = new_vector[i];
I only dabble with C++, so apologies if I am asking basic questions.
Thanks

Answer 1

If you already know that the 1st argument is the one to use it's simple, copy it to a string and then access it using one of the iteration options given by C++, I'm using a foreach type cycle:
#include <iostream>
#include <vector>
int main(int argc, char** argv)
{
if(argc < 2){
std::cout << "Not enough arguments"; //<-- args check
return 0;
}
std::string s1;
s1 = argv[1]; //<-- copy argument to a string type to use string iterator
std::vector<int> args_vector;
for (char c : s1) {
args_vector.push_back(c - '0'); // convert char to integer and save it in vector
}
for(int i: args_vector){ // print the args in integer format, 1 by 1
std::cout << i << " ";
}
return 0;
}

Answer 2

You could create strings out of the arguments and just go though them character by character:
#include <iostream>
#include <string>
#include <vector>
int cppmain(std::string program, std::vector<std::string> args) {
std::cout << program << " got " << args.size() << " argument(s):\n";
for(auto& arg : args) { // each argument as a string
std::cout << " " << arg << '\n';
for(char ch : arg) { // each char in the current argument
if(ch < 0) continue; // skip negative char:s
int in_arg = m[ch]; // assuming it was: int in_arg = m[*argv[i]];
// use in_arg
}
}
return 0;
}
int main(int argc, char* argv[]) {
//
// string from char*
// |
// V
return cppmain(argv[0], {argv + 1, argv + argc});
// ^ ^
// | |
// vector<string> from char*[]
}