| | void *
bst_t_prev (struct bst_traverser *trav)
{
struct bst_node *x;
assert (trav != NULL);
if (trav->bst_generation != trav->bst_table->bst_generation)
trav_refresh (trav);
x = trav->bst_node;
if (x == NULL)
{
return bst_t_last (trav, trav->bst_table);
}
else if (x->bst_link[0] != NULL)
{
if (trav->bst_height >= BST_MAX_HEIGHT)
{
bst_balance (trav->bst_table);
return bst_t_prev (trav);
}
trav->bst_stack[trav->bst_height++] = x;
x = x->bst_link[0];
while (x->bst_link[1] != NULL)
{
if (trav->bst_height >= BST_MAX_HEIGHT)
{
bst_balance (trav->bst_table);
return bst_t_prev (trav);
}
trav->bst_stack[trav->bst_height++] = x;
x = x->bst_link[1];
}
}
else
{
struct bst_node *y;
do
{
if (trav->bst_height == 0)
{
trav->bst_node = NULL;
return NULL;
}
y = x;
x = trav->bst_stack[--trav->bst_height];
}
while (y == x->bst_link[0]);
}
trav->bst_node = x;
return x->bst_data;
}
|
