how to make a n*n 2d dynamic array in c++

int** a = new int*[rowCount];
for(int i = 0; i < rowCount; ++i)
    a[i] = new int[colCount];

for (int i = 0; i < numRows; i++) {
    delete [] world[i];
//    world[i] = 0;  // <- don't have to do this
}
delete [] world;  // <- because they won't exist anymore after this
world = 0;

int** arr = new int*[10]; // Number of Students
int i=0, j;
for (i; i<10; i++) 
	arr[i] = new int[5]; // Number of Courses
In line[1], you're creating an array which can store the addresses
  of 10 arrays. In line[4], you're allocating memories for the 
  array addresses you've stored in the array 'arr'. So it comes out 
  to be a 10 x 5 array.