Create binary search tree 01-intro.cpp

Author: Venkat-Gorla

binary-search-tree/01-intro.cpp

@@ -0,0 +1,161 @@
+//----------------------------------------
+// Binary search tree
+// Topics covered:
+// - tree creation, node insertion with and without recursion
+
+#include <iostream>
+#include <vector>
+using namespace std;
+
+struct Node
+{
+ int data;
+ Node* left;
+ Node* right;
+};
+
+Node* Create(int value)
+{
+ return new Node{value, nullptr, nullptr};
+}
+
+// recursive insert function for bst
+Node* rInsert(Node* root, int value)
+{
+ if (root == nullptr)
+ return Create(value);
+
+ if (value < root->data)
+ {
+ root->left = rInsert(root->left, value);
+ }
+ else if (value > root->data)
+ {
+ root->right = rInsert(root->right, value);
+ }
+ else
+ {
+ // ignore dupe values; an alternate solution is to have a ref count
+ // inside every node and increment it when we get a dupe value
+ }
+
+ return root;
+}
+
+// wrapper function to create bst from a list of keys
+Node* rCreate(const vector<int> & input)
+{
+ Node* root = nullptr;
+ for (auto value : input)
+ root = rInsert(root, value);
+
+ return root;
+}
+
+// bst insert function without using recursion
+Node* Insert(Node* root, int value)
+{
+ if (root == nullptr)
+ return Create(value);
+
+ Node* current = root;
+ while (true)
+ {
+ if (value == current->data)
+ {
+ // dupe value, ignore
+ break;
+ }
+
+ if (value < current->data)
+ {
+ if (current->left == nullptr)
+ {
+ current->left = Create(value);
+ break;
+ }
+ else
+ {
+ current = current->left;
+ }
+ }
+ else
+ {
+ if (current->right == nullptr)
+ {
+ current->right = Create(value);
+ break;
+ }
+ else
+ {
+ current = current->right;
+ }
+ }
+ }
+
+ return root;
+}
+
+// wrapper function
+Node* Create(const vector<int> & input)
+{
+ Node* root = nullptr;
+ for (auto value : input)
+ root = Insert(root, value);
+
+ return root;
+}
+
+// for testing
+void Inorder(Node* root)
+{
+ if (root)
+ {
+ Inorder(root->left);
+ cout << root->data << " ";
+ Inorder(root->right);
+ }
+}
+
+void testcase(const vector<int> & input)
+{
+ {
+ auto root = rCreate(input);
+ cout << "Inorder traversal of bst created using recursion is ";
+ Inorder(root);
+ cout << endl;
+ }
+
+ {
+ auto root = Create(input);
+ cout << "Inorder traversal of bst created *WITHOUT* recursion is ";
+ Inorder(root);
+ cout << endl;
+ }
+}
+
+int main(int argc, char *argv[])
+{ 
+ {
+ /*
+ 3 
+ / \
+ 1 5 
+ \ /
+ 2 4 
+
+ */
+
+ const vector<int> input{3, 1, 2, 5, 4};
+ testcase(input);
+ }
+
+ return 0;
+}
+
+/*
+Output:
+Inorder traversal of bst created using recursion is 1 2 3 4 5
+Inorder traversal of bst created *WITHOUT* recursion is 1 2 3 4 5
+
+*/