Create 01 - Recursive Approach.cpp

Author: JawadSher

24 - Dynamic Programming Problems/28 - Unique Binary Search Trees/01 - Recursive Approach.cpp

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+class Solution {
+public:
+    int numTrees(int n) {
+        // Base case: If there are 0 or 1 nodes, there is only 1 unique BST possible.
+        if(n <= 1) return 1;
+
+        int ans = 0; // Initialize the variable to store the total number of unique BSTs.
+
+        // Loop through each number i from 1 to n.
+        // Treat 'i' as the root of the BST.
+        for(int i = 1; i <= n; i++) {
+            // Recursively calculate the number of unique BSTs for the left and right subtrees.
+            // Left subtree has (i-1) nodes.
+            // Right subtree has (n-i) nodes.
+            ans += numTrees(i-1) * numTrees(n-i);
+        }
+
+        // Return the total count of unique BSTs for n nodes.
+        return ans;
+    }
+};