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Fixes: #2706: Create a balanced binary search tree from a sorted array. #2711

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Merged
merged 2 commits into from
Oct 26, 2021
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Fixes: #2706: Create a balanced binary search tree from a sorted array. #2711

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ed034ff
Fixes: #2706: Create a balanced binary search tree from a sorted array.
akumar-indeed Oct 23, 2021
a48c12d
Merge branch 'master' into jira/CreateBSTFromSortedArray
siriak Oct 26, 2021
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Fixes: #2706: Create a balanced binary search tree from a sorted array.
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@akumar-indeed
akumar-indeed committed Oct 23, 2021
commit ed034ffb16a23a16d886454091178c58623f9910
7 changes: 6 additions & 1 deletion DataStructures/Trees/BinaryTree.java
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Original file line number Diff line number Diff line change
Expand Up @@ -19,7 +19,7 @@ public class BinaryTree {
*
* @author Unknown
*/
class Node {
static class Node {
/** Data for the node */
public int data;
/** The Node to the left of this one */
Expand Down Expand Up @@ -50,6 +50,11 @@ public BinaryTree() {
root = null;
}

/** Parameterized Constructor */
public BinaryTree(Node root) {
this.root = root;
}

/**
* Method to find a Node with a certain value
*
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45 changes: 45 additions & 0 deletions DataStructures/Trees/CreateBSTFromSortedArray.java
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@@ -0,0 +1,45 @@
package DataStructures.Trees;

import DataStructures.Trees.BinaryTree.Node;

/**
* Given a sorted array. Create a balanced binary search tree from it.
*
* Steps:
* 1. Find the middle element of array. This will act as root
* 2. Use the left half recursively to create left subtree
* 3. Use the right half recursively to create right subtree
*/
public class CreateBSTFromSortedArray {

public static void main(String[] args) {
test(new int[]{});
test(new int[]{1, 2, 3});
test(new int[]{1, 2, 3, 4, 5});
test(new int[]{1, 2, 3, 4, 5, 6, 7});
}

private static void test(int[] array) {
BinaryTree root = new BinaryTree(createBst(array, 0, array.length - 1));
System.out.println("\n\nPreorder Traversal: ");
root.preOrder(root.getRoot());
System.out.println("\nInorder Traversal: ");
root.inOrder(root.getRoot());
System.out.println("\nPostOrder Traversal: ");
root.postOrder(root.getRoot());
}

private static Node createBst(int[] array, int start, int end) {
// No element left.
if (start > end) {
return null;
}
int mid = start + (end - start) / 2;

// middle element will be the root
Node root = new Node(array[mid]);
root.left = createBst(array, start, mid - 1);
root.right = createBst(array, mid + 1, end);
return root;
}
}