Question

This code should ask the user for a their name and then split it at the space.

It should put the firstname in the variable first, and the last name in de variable lastname

#include <iostream>

using namespace std;

int main()
{
char string[80];
char first[20];
char lastname[20];
bool f = true;
int c = 0;
cout << "Whats your Name? \n";
gets(string);

for(int i =0; i < strlen(string); i++){
    if(string[i] == ' ') {
        f = false;
        c = 0;
    }

    if(f) {
        first[c] = string[i];
    } else if(!f) {
        lastname[c] = string[i];
    }


    c++;
}

for(int i = 0; i < strlen(first); i++) {
    cout << first[i] << "\n";
}
for(int i = 0; i < strlen(lastname); i++) {
    cout << lastname[i]<< "\n";
}

return 0;
}

Answer 1

Unless you really need to write this using only C functions, it would be much easier to use C++ strings.

Something like (this is untested):

std::string input;
std::string first;
std::string lastname;

// prompt the user
std::cout << "What's your name? ";
// get a line of input
std::getline(std::cin, input);

// find a space in the string
size_t space = input.find_first_of(" ");
// was the space found?
if (space != std::string::npos)
{
    // copy out the first and last names
    first = input.substr(0, space);
    lastname = input.substr(space + 1);

    // output them to stdout
    std::cout << first << std::endl << lastname << std::endl;
}

This means you don’t have to worry about null-terminating strings or string lengths or anything like that. As flolo said, your code doesn’t do that and thus will definitely run into problems. The memory layout of a C string is an array of characters with a null byte on the end, which is how things like strlen() know where the end of the string is. Also, your code’s going to have a horrible time the moment somebody enters a name with more than 20 characters in it, which isn’t particularly implausible.