From ffb45c604aa33998023ea56be89b50e6a12821a1 Mon Sep 17 00:00:00 2001
From: Kamini Prajapati <kaminiprajapati727@gmail.com>
Date: Mon, 28 Oct 2024 16:39:05 +0530
Subject: [PATCH] done

---
 .../Check if a Tree is a BST or not/Program.c | 51 +++++++++++++++++++
 .../Check if a Tree is a BST or not/README.md | 19 +++++++
 2 files changed, 70 insertions(+)
 create mode 100644 Binary Tree Algorithms/Check if a Tree is a BST or not/Program.c
 create mode 100644 Binary Tree Algorithms/Check if a Tree is a BST or not/README.md

diff --git a/Binary Tree Algorithms/Check if a Tree is a BST or not/Program.c b/Binary Tree Algorithms/Check if a Tree is a BST or not/Program.c
new file mode 100644
index 00000000..cfdef368
--- /dev/null
+++ b/Binary Tree Algorithms/Check if a Tree is a BST or not/Program.c	
@@ -0,0 +1,51 @@
+#include <stdio.h>
+#include <stdbool.h>
+#include <limits.h>
+
+struct Node {
+    int data;
+    struct Node* left;
+    struct Node* right;
+};
+
+// Function to create a new node
+struct Node* newNode(int data) {
+    struct Node* node = (struct Node*)malloc(sizeof(struct Node));
+    node->data = data;
+    node->left = node->right = NULL;
+    return node;
+}
+
+// Utility function to check BST properties
+bool isBSTUtil(struct Node* node, int min, int max) {
+    if (node == NULL)
+        return true;
+
+    // Node's value must lie between min and max
+    if (node->data <= min || node->data >= max)
+        return false;
+
+    // Recursively check left and right subtrees
+    return isBSTUtil(node->left, min, node->data) &&
+           isBSTUtil(node->right, node->data, max);
+}
+
+// Main function to check if a tree is a BST
+bool isBST(struct Node* root) {
+    return isBSTUtil(root, INT_MIN, INT_MAX);
+}
+
+int main() {
+    struct Node* root = newNode(10);
+    root->left = newNode(5);
+    root->right = newNode(20);
+    root->left->left = newNode(3);
+    root->left->right = newNode(8);
+    
+    if (isBST(root))
+        printf("The tree is a Binary Search Tree\n");
+    else
+        printf("The tree is not a Binary Search Tree\n");
+
+    return 0;
+}
diff --git a/Binary Tree Algorithms/Check if a Tree is a BST or not/README.md b/Binary Tree Algorithms/Check if a Tree is a BST or not/README.md
new file mode 100644
index 00000000..89e67e9e
--- /dev/null
+++ b/Binary Tree Algorithms/Check if a Tree is a BST or not/README.md	
@@ -0,0 +1,19 @@
+The function recursively verifies that each node’s value lies within a specific range, ensuring all nodes in the left subtree are less and all nodes in the right subtree are greater than the current node.
+
+Explanation of the Code
+
+isBSTUtil Function:
+->This recursive utility function checks whether each node’s value is within a specific range (min to max).
+->It checks if the current node's value violates the range conditions.
+->It then recursively checks left and right subtrees with updated ranges to maintain BST constraints.
+
+isBST Function:
+->This function initializes the range for the root node using INT_MIN and INT_MAX, covering all integer values.
+
+Main Function:
+->We create a sample tree and test if it’s a BST by calling isBST.
+
+This approach runs in O(n)
+
+O(n) time complexity, where n is the number of nodes, and it uses O(h) space for recursion, where 
+h is the height of the tree.
\ No newline at end of file