CODEWITHSUNDEEP
c++integer
cppcoder
cppcoder

Reputation: 23135

How to get a 2d int array from a char*?

I want to pass a 2d int array into a main function. Since the main function signature is like this int main(int argc, char*argv[] How can I get the 2d array into a int[][] in my code?

Command line: myprogram {{2,3},{5,6},{4,5},{6,8},{2,5}}

Upvotes: 0

Views: 362

Answers (3)

A. K.
A. K.

Reputation: 38234

You need to parse the command line input that you give to the program. That might be slightly involved.

What you can do is--since you know that that array is gonna be a 2D array. Pass the command line input like this:

myprogram < number of rows(r) > < number of columns(c) > n_1 n_2 n_3 .... n_(r*c)

where ns are the elements of your array in 'row-major' fashion.

In this way you code to read the command line input will be much simpler.

Otherwise if you want to retain the format of input. You have to build a 'small' parser to read those input. Basically you have 5 'kinds' of characters that you need to deal with:

  1. right brace '} '
  2. left brace '{'
  3. digits[0-9]
  4. comma ','
  5. space ' '

Handling space will be little bit tricky because with each space in the command line input argc increments by one.

EDIT: You may follow upon these lines. NB: This code may have errors and some logic also needs to be checked, but this can be a starting point for you to start parsing the command line input in the format that you have given. 

int main()
{
int count = 1;
std::vector<vector<int>> arr2d;
std::vector<int> arr1d;
std::string buf;
while(count<argc) {
  //accumulate what all you get from command line into string
  buf += argv[count];
  count++;
}
std::string curr_num;
int num_elements;
int i = 0;
int lparen=0,rparen=0,nrows=0;
char c;
while(i<buf.length()){
  c = buf[i];
  switch(c) {
  case '{':
    lparen++;
    break;
  case '}':
    rparen++;
    nrows++;
    arr2d.push_back(arr1d);
    arr1d.clear();
    break;
  case ' ':
    break;
  case ',':
    num_elements++;
    if(curr_num.length() != 0) {
      //i'm not sure this will work but you have to do something similar
      arr1d.push_back((int)curr_num.c_str());
    }
    else {//do some error handling}
  case '0':
  //....
  case '9':
    curr_num += buf[i];
  break;
  default:
  //throw error;
  //there might be other checks you may feel like doing 
  //you'll get better idea as you start writing on your own.
}
i++;
}
if(lparen || rparen)
  //throw error ...
 //...
return 0;
}

Upvotes: 0

Seb Holzapfel
Seb Holzapfel

Reputation: 3873

The main() function takes either nothing or command-line arguments as char *s - you can't just give it whatever you please! You would have to parse the char * to get the data you need.

Do you have to enter information in that fashion, though? If it were entered like this (just through cin, not command-line arguments:

1 2 3
4 5 6
7 8 9

You could assign it to an int a[][] using something like this:

int main() 
{
    const int X=3, Y=3;
    int a[X][Y];
    string currentLine;

    for(int i = 0; i != X; ++i) {
        getline(cin, currentLine);
        istringstream currentInput(currentLine);
        for(int j = 0; j != Y; ++j)
            currentInput >> a[i][j];
    }

    return 0;
}

Upvotes: 0

Ariel
Ariel

Reputation: 26783

This: {{2,3},{5,6},{4,5},{6,8},{2,5}} will end up as a string in your program. You will need to break it up into pieces yourself to turn it into an array of arrays.

Upvotes: 5

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