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#include "tst.h"
#include <stdio.h>
#include <stdlib.h>
void *tst_delete(unsigned char *key, struct tst *tst)
{
struct node *current_node;
struct node *current_node_parent;
struct node *last_branch;
struct node *last_branch_parent;
struct node *next_node;
struct node *last_branch_replacement;
struct node *last_branch_dangling_child;
int key_index;
if(key[0] == 0)
return NULL;
if(tst->head[(int)key[0]] == NULL)
return NULL;
last_branch = NULL;
last_branch_parent = NULL;
current_node = tst->head[(int)key[0]];
current_node_parent = NULL;
key_index = 1;
while(current_node != NULL)
{
if(key[key_index] == current_node->value)
{
if( (current_node->left != NULL) || (current_node->right != NULL) )
{
last_branch = current_node;
last_branch_parent = current_node_parent;
}
if(key[key_index] == 0)
break;
else
{
current_node_parent = current_node;
current_node = current_node->middle;
key_index++;
continue;
}
}
else if( ((current_node->value == 0) && (key[key_index] < 64)) ||
((current_node->value != 0) && (key[key_index] <
current_node->value)) )
{
last_branch_parent = current_node;
current_node_parent = current_node;
current_node = current_node->left;
last_branch = current_node;
continue;
}
else
{
last_branch_parent = current_node;
current_node_parent = current_node;
current_node = current_node->right;
last_branch = current_node;
continue;
}
}
if(current_node == NULL)
return NULL;
if(last_branch == NULL)
{
next_node = tst->head[(int)key[0]];
tst->head[(int)key[0]] = NULL;
}
else if( (last_branch->left == NULL) && (last_branch->right == NULL) )
{
if(last_branch_parent->left == last_branch)
last_branch_parent->left = NULL;
else
last_branch_parent->right = NULL;
next_node = last_branch;
}
else
{
if( (last_branch->left != NULL) && (last_branch->right != NULL) )
{
last_branch_replacement = last_branch->right;
last_branch_dangling_child = last_branch->left;
}
else if(last_branch->right != NULL)
{
last_branch_replacement = last_branch->right;
last_branch_dangling_child = NULL;
}
else
{
last_branch_replacement = last_branch->left;
last_branch_dangling_child = NULL;
}
if(last_branch_parent == NULL)
tst->head[(int)key[0]]=last_branch_replacement;
else
{
if (last_branch_parent->left == last_branch)
last_branch_parent->left = last_branch_replacement;
else if (last_branch_parent->right == last_branch)
last_branch_parent->right = last_branch_replacement;
else
last_branch_parent->middle = last_branch_replacement;
}
if(last_branch_dangling_child != NULL)
{
current_node = last_branch_replacement;
while (current_node->left != NULL)
current_node = current_node->left;
current_node->left = last_branch_dangling_child;
}
next_node = last_branch;
}
do
{
current_node = next_node;
next_node = current_node->middle;
current_node->left = NULL;
current_node->right = NULL;
current_node->middle = tst->free_list;
tst->free_list = current_node;
}
while(current_node->value != 0);
return next_node;
}
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