# About an indefinite matrix

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• 11-19-2006
nick048
About an indefinite matrix
Hi to All,

I need to fill a matrix as this:
Code:

`char mat [N] [N]`
N is an integer, that I don't know.
In my program I have a construct for its Input as this.
Code:

`cin >> N;`
Can work this scenario ?

For Example can work this program?
Code:

```#include <iostream.h>   int main() {   int N;  /max element for Matrix   char mat[N][N];   int i, j; /Counters     cout << 'Enter the number of Rows and Colums ';   cin >> N;   cout << endl;     cout << 'Enter the Matrix elements ' << endl;     for (i=0; i<N; i++)   {   for (j=0; j<N; j++)   cout << mat[i][j];       cout << endl;   }   cout << endl;   }```
This code is correct ? How can resolve my problem ?

Thank you for help. Be patient with me; I am new in c++ programming.

Best Regards
• 11-19-2006
vart
1. use <iostream>
2. use vector of vectors
3. Check value entered by the user before using it
4. Don't use variables without initializing them
• 11-19-2006
nick048
Quote:

Originally Posted by vart
2. use vector of vectors

Hi,
Thank You for fast reply.
Please, what is vector of vectors ?
Have You a sample or a link, in order to learn this concept ?

Best Regards
• 11-19-2006
laserlight
Quote:

Please, what is vector of vectors ?
In your context, it would be:
Code:

`std::vector<std::vector<char> > mat;`
You would need to #include <vector>, of course.
• 11-19-2006
jlf029
If you still want to use your char array you must make it dynamic otherwise your compiler expects a constant.
For example:

Code:

```cin >> N; char** mat = new char*[N]; for(int i=0;i<N;i++)     mat[i] = new char[N];```