Create Construct BST

Author: akshayavb99

Course 2 - Data Structures in JAVA/Lecture 13 - BST I/Construct BST

@@ -0,0 +1,52 @@
+/*
+Given a sorted integer array A of size n, which contains all unique elements. You need to construct a balanced BST from this input array. Return the root of constructed BST.
+Note: If array size is even, take first mid as root.
+
+Input format:
+The first line of input contains an integer, which denotes the value of n. The following line contains n space separated integers, that denote the values of array.
+
+Output Format:
+The first and only line of output contains values of BST nodes, printed in pre order traversal.
+
+Constraints:
+Time Limit: 1 second
+
+Sample Input 1:
+7
+1 2 3 4 5 6 7
+Sample Output 1:
+4 2 1 3 6 5 7 
+*/
+public class Solution {
+
+	/*	Binary Tree Node class 
+	 * 
+	 * 	class BinaryTreeNode<T> {
+			T data;
+			BinaryTreeNode<T> left;
+			BinaryTreeNode<T> right;
+			
+			public BinaryTreeNode(T data) {
+				this.data = data;
+			}
+		}
+		*/
+	
+		public static BinaryTreeNode<Integer> SortedArrayToBST(int[] arr, int n){
+            return SortedArrayToBSTHelper(arr,0,n-1);
+			
+		}
+    
+        public static BinaryTreeNode<Integer> SortedArrayToBSTHelper(int[] arr, int si, int ei){
+            if (si>ei)
+                return null;
+            
+            int mid=(si+ei)/2;
+            BinaryTreeNode<Integer> root = new BinaryTreeNode<Integer>(arr[mid]);
+            
+            root.left=SortedArrayToBSTHelper(arr,si,mid-1);
+            root.right=SortedArrayToBSTHelper(arr,mid+1,ei);
+            return root;
+			
+		}
+	}