#define pow2(n) (1 << (n))

/* função recebe o nó raiz da árvore */

void btree_print_node_graph(btree_node *node) {
    if (node == NULL) {
        return;
    }
    else {
        char fmt[9];
        btree_node **row1, **row2, **row_tmp;
        size_t rows, row, col;

    /* é necessário ter uma função que retorne a altura da árvore */
        rows = btree_height(node);

        row1 = malloc(sizeof(btree_node *) * pow2(rows));
        row2 = malloc(sizeof(btree_node *) * pow2(rows));
        row1[0] = node;
        for (row = 0; row < rows; row++) {
            size_t col2 = 0, cols = pow2(row);
            sprintf(fmt, "%%%dc", pow2(rows - (row + 1)));
            for (col = 0; col < cols; col++) {
                btree_node *n = row1[col];
                if (n != NULL) {
                    /* altere aqui o nome dos campos */
                    printf(fmt, *(char *) n->data);
                    row2[col2++] = n->left;
                    row2[col2++] = n->right;
                }
                else {
                    printf(fmt, ' ');
                    row2[col2++] = NULL;
                    row2[col2++] = NULL;
                }
                if (!col) {
                    sprintf(fmt, "%%%dc", pow2(rows - (size_t)(row)));
                }
            }
            printf("\n");
            row_tmp = row1;
            row1 = row2;
            row2 = row_tmp;
        }
        free(row1);
        free(row2);
    }
}