how to write multidimensional array in c++ code example

Example 1: loop over multidimensional array c++

int arr[2][3] = {
  {1,2,3}, 
  {4,5,6}
};
for(int i=0 ; i<sizeof(arr) / sizeof(arr[0]) ; i++){
	for(int j=0 ; j<sizeof(arr[i])/sizeof(arr[i][0]) ; j++){
		cout<<"2D array have: "<< arr[i][j]<<endl;
	}
}

Example 2: c++ code to write 2d array

#include <iostream>
using namespace std;
int main(){
	int n,m;
	int a[n][m];
	cin >> n >>m;
	for ( int i=0; i<n; i++){
		for (int j=0; j<m; j++){
			cin >> a[i][j];
		}
	}
	
	for ( int x=0; x<n; x++){
		for (int y=0; y<m; y++){
			cout << "a[" << x << "][" << y << "]: ";
			cout << a[x][y] << endl;
		}
	}
	return 0;
}