Want to specify a specific character in a char array

Question

I have made a char array, where I basically enter the number of rows and columns, and enter in the letters for each row and column, such as x and y. Basically, like an normal array but with letters. After I enter the letters and finish with the array, I want to enter 2 numbers to specify a specific char in the array. For example, my array is 3x3. I fill my array with the characters x and y. After I do that, I enter 2 2. At row 2 and column 2, the letter there is y. So I want to print out y.

Here is my code.

#include <iostream>

using namespace std;

int main()
{
  int x,y;
  cin>>x>>y;
  char n[x][y];
  for(int i=0;i<x;i++)
  {
      for(int j=0;j<y;j++)
      {
          cin>>n[i][j];
      }
  }
  int a,b;
  cin>>a>>b;
  cout<<n[a][b];
}

Answer 1

The main problem with your given program is that in Standard C++ the size of an array must be a compile time constant. This means that the following is not valid:

int x,y;
cin>>x>>y;
char n[x][y];//not standard C++ because x and y are not constant expressions

To solve this you can use a std::vector<char> as shown below:

#include <iostream>
#include<vector>


int main()
{
  int x,y;
  std::cin>>x>>y;
  //create a 2D vector
  std::vector<std::vector<char>> n(x, std::vector<char>(y)); 
  
  //iterate through rows 
  for(auto& row: n)
  {
      //iterate through each element in the row
      for(auto& col: row)
      {
          std::cout<<"enter element: "<<std::endl;
          std::cin>>col; //take input from user
      }
  }
  int a,b;
  std::cout<<"a and b"<<std::endl;
  std::cin>>a>>b;
  std::cout<<"element at position: "<<a<<" "<<b <<" is: "<<n[a][b];
}

Working demo