Print a binary tree

print-binary-tree.c

void padding ( char ch, int n ){
  int i;
  
  for ( i = 0; i < n; i++ )
    putchar ( ch );
}

void structure ( struct node *root, int level ){
  int i;
  
  if ( root == NULL ) {
    padding ( '\t', level );
    puts ( "~" );
  } else {
    structure ( root->right, level + 1 );
    padding ( '\t', level );
    printf ( "%d\n", root->info );
    structure ( root->left, level + 1 );
  }
}

int main ( void ){
  struct node *tree = NULL;
  /* ... */
  structure ( tree, 0 );
  /* ... */
}

void structure ( struct node *root, int level ){ int i;
what does int i; stand for?

It's useless.