storing a string to a 2d char array - c++

Question

I am trying to store a sentence to a 2d array by separating each words. In the 2d array each row will contain each word from the sentence. Here is what I think I should do.
//Logic
//given string mystring
string mystring = "testing the arrays";
//create a 2d char array to hold 4 words with 10 max size
char 2darr[4][10] = {" "};
int x = 0;
for (int i = 0,j=0; i <mystring.length(); i++)
{
if (mystring(i) != ' ')
2darr[x][j++] = mystring(i); //copy the each character to the first row
else
2darr[x][j++] = '\0';
++x; // goes to next row
j = 0; //reset j for new row
}
Is there a better way to do this? I think my logic is a little off as well

Answer 1

The better way to do this is:
1) There is no need to check spaces. For this to occur, you can use std::istringstream with operator >> to obtain each word in a loop.
2) Use strncpy to copy the string into the 2 dimensional array
3) You need to make sure that the string does not exceed the bounds of the array, and that you have no more than 4 separate words.
Here is an example:
#include <iostream>
#include <string>
#include <vector>
#include <sstream>
#include <cstring>
int main()
{
char arr2d[4][10] = {};
std::string mystring = "testing the arrays";
// create an input stream containing the test string
std::istringstream strm(mystring);
std::string word;
// this is the word count
int curCount = 0;
// obtain each word and copy to the array
while (strm >> word && curCount < 4)
strncpy(arr2d[curCount++], word.c_str(), 9);
// output the results
for (int i = 0; i < curCount; ++i)
std::cout << arr2d[i] << "\n";
}
Output:
testing
the
arrays

Answer 2

this expression char 2darr[4][10] = {" "} will only set the first element to be " ", the others will be '\0' or NULL. But it is probably OK, since it is the default terminator of C-strings.
Variables can't start with a digit, call it arr2d instead.
String character access is mystring[i], not mystring(i)
You only indented the lines in the else block, in C++ if you don't enclose a block with curly braces, it only captures the first row, what you basically wrote is:
else {
2darr[x][j++] = '\0';
}
++x; // goes to next row
j = 0; //reset j for new row
Corrected code is
std::string mystring = "testing the arrays";
//create a 2d char array to hold 4 words with 10 max size
char arr2d[4][10] = { };
int x = 0;
for (int i = 0, j = 0; i < mystring.length(); i++)
{
if (mystring[i] != ' ') {
arr2d[x][j++] = mystring[i]; //copy the each character to the first row
}
else {
arr2d[x][j++] = '\0';
++x; // goes to next row
j = 0; //reset j for new row
}
}