given n, construct possible number of BST trees

Author: manju07

Data-Structure/Tree/Binary Search Tree/Construction and Conversion/constructTrees.js

@@ -0,0 +1,45 @@
+'use strict';
+class Node {
+    constructor(data) {
+        this.data = data;
+        this.leftNode = this.rightNode = null;
+    }
+}
+
+function constructTrees(start, end) {
+    let list = [];
+    if (start > end) {
+        list.push(null);
+        return list;
+    }
+    for (let i = start; i <= end; i++) {
+        let leftList = constructTrees(start, i - 1);
+        let rightList = constructTrees(i + 1, end);
+        for (let j = 0; j < leftList.length; j++) {
+            let leftNode = leftList[j];
+            for (let k = 0; k < rightList.length; k++) {
+                let rightNode = rightList[k];
+                let temp = new Node(i);
+                temp.leftNode = leftNode;
+                temp.rightNode = rightNode;
+                list.push(temp);
+            }
+        }
+    }
+    return list;
+}
+
+function preOrderDisplay(root, preOrderArr) {
+    if (root == null) return;
+    preOrderArr.push(root.data);
+    preOrderDisplay(root.leftNode, preOrderArr);
+    preOrderDisplay(root.rightNode, preOrderArr);
+}
+
+let BSTTrees = constructTrees(1, 3);
+let preOrderArr = [];
+for (let index = 0; index < BSTTrees.length; index++) {
+    preOrderArr = [];
+    preOrderDisplay(BSTTrees[index], preOrderArr);
+    console.log('preOrder Display - ', preOrderArr.join(' ,'));
+}