Count total number of vertical columns in a Binary Tree

Every node in a binary tree can be considered belonging to a column. If we assume that 'root' belongs to column '0' then root->left belongs to column '-1', root->right belongs to column '+1' and root->left->right belongs to column '0' and so on. We have to find the total number of such columns.

void totalCol(struct node* root, int col, int* minC, int* maxC)
{
    if(root == NULL)
        return;

    totalCol(root->left, col-1, minC, maxC);
    totalCol(root->right, col+1, minC, maxC);

    *minC = MIN(*minC, col);
    *maxC = MAX(*maxC, col);
}

int main()
{
    struct node *root=NULL;

    int minC=0;
    int maxC=0;

    insert(&root, 50);
    insert(&root, 25);
    insert(&root, 100);
    insert(&root, 30);
    insert(&root, 10);
    insert(&root, 5);

    totalCol(root, 0, &minC, &maxC);

    printf("Total Col: %d\n", maxC - minC + 1);

    return 0;
}