Question

this code will good for n<20, but for n=40 give me access violation error:
this code will fill X and O random.

 int i=0,j=0;
 int x=0,y=0;
 int n=40;
 for(i=0;i<n;i++)
 {
     for(j=0;j<n;j++)
         arr[i][j]='O';
 }

 srand(clock());
 for(i=0;i<n*n;i++)
 {
   x = rand()%n;
   y = rand()%n;
   if(arr[x][y] == 'O') arr[x][y]='X';
 }

Declare:

 arr = (char**)malloc(n);
 for(i=0;i<n;i++)
    arr[i] = (char*)malloc(n);

Answer 1

change

arr = (char**)malloc(n);

to

arr = (char**)malloc(n*sizeof(char*));