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#include <cstddef>
#include <cstdlib>
#include <ctime>
#include <iostream>
#include <ostream>
class BinarySearchTree
{
struct Node
{
int data;
Node *parent;
Node *left_child;
Node *right_child;
explicit Node(int data, Node *parent = NULL):
data(data),
parent(parent),
left_child(NULL),
right_child(NULL)
{
}
~Node()
{
delete left_child;
delete right_child;
}
};
public:
BinarySearchTree():
root(NULL),
sz(0)
{
std::srand(std::time(NULL));
}
~BinarySearchTree()
{
delete root;
}
bool empty() const
{
return sz == 0;
}
std::size_t size() const
{
return sz;
}
void insert(int nd) // nd = Node Data
{
if (root != NULL)
{
Node *temp = root;
while (true)
if (nd < temp>data)
{
if (temp>left_child == NULL)
{
temp>left_child = new Node(nd, temp);
break;
}
else
temp = temp>left_child;
}
else
if (nd > temp>data)
{
if (temp>right_child == NULL)
{
temp>right_child = new Node(nd, temp);
break;
}
else
temp = temp>right_child;
}
else // nd == temp>data
return; // nothing to insert
}
else
root = new Node(nd);
++sz;
}
void remove(int nd) // nd = Node Data
{
if (root == NULL)
return;
Node *target = root;
bool found_nd = false;
while (true)
if (nd < target>data)
{
if (target>left_child != NULL)
target = target>left_child;
else
break;
}
else
if (nd > target>data)
{
if (target>right_child != NULL)
target = target>right_child;
else
break;
}
else // nd == target>data
{
found_nd = true;
break;
}
// target wasn't found, nothing to remove
if (!found_nd)
return;
kill_node(target);
sz;
}
void display(std::ostream &os = std::clog) const
{
os << "BinarySearchTree @ " << this << ", size: " << sz << '\n';
recursive_display_on(os, root);
}
void recursive_display_on(std::ostream &os, const Node *n) const
{
if (n == NULL)
return;
recursive_display_on(os, n>left_child);
os << n>data << ' ';
recursive_display_on(os, n>right_child);
}
private:
void kill_node(Node *target)
{
// according to Wikipedia, we must now deal with three cases:
// (1) no children
// (2) one child
// (3) two children
// case (1)
if (target>left_child == NULL && target>right_child == NULL)
{
if (target>parent == NULL) // this can only be the root node
{
delete root;
root = NULL;
}
else
// determine if `target' is a left child, or a right child
if (target>parent>data < target>data)
target>parent>right_child = NULL;
else
target>parent>left_child = NULL;
delete target;
}
else
// case (2)
if (target>left_child == NULL && target>right_child != NULL)
{
target>data = target>right_child>data;
delete target>right_child;
target>right_child = NULL;
}
else
if (target>left_child != NULL && target>right_child == NULL)
{
target>data = target>left_child>data;
delete target>left_child;
target>left_child = NULL;
}
else
// case (3)
{
// according to Wikipedia, we shouldn't be "consistent" in choosing
// between inorder predecessor and inorder successor
if (std::rand() % 2 == 0) // go for predecessor
{
Node *p = target>left_child;
while (p>right_child != NULL)
p = p>right_child;
target>data = p>data;
kill_node(p);
}
else // go for successor
{
Node *s = target>right_child;
while (s>left_child != NULL)
s = s>left_child;
target>data = s>data;
kill_node(s);
}
}
}
Node *root;
std::size_t sz;
};
int main()
{
BinarySearchTree bst;
// bst.remove(27);
bst.insert(1);
bst.insert(5);
bst.insert(90);
bst.insert(0);
bst.insert(90);
bst.insert(25);
bst.insert(2);
bst.insert(2);
bst.insert(2);
bst.insert(23);
bst.insert(24);
// bst.remove(90);
// bst.remove(1);
// bst.remove(90);
// bst.remove(25);
bst.insert(3);
bst.display();
}
 