201st Commit

README.md

@@ -196,9 +196,10 @@ Ace Coding Interview with 75 Qs
 | Binary Search Tree                  |                 |        |
 | ----------------------------------- | --------------- | ------ |
 | 700. Search in a Binary Search Tree | [Solution][700] | Easy   |
-| 450. Delete Node in a BST           | Solution        | Medium |
+| 450. Delete Node in a BST           | [Solution][450] | Medium |
 
 [700]: ./src/page-7/700.%20Search%20in%20a%20Binary%20Search%20Tree/searchBST.ts
+[450]: ./src/page-5/450.%20Delete%20Node%20in%20a%20BST/deleteNode.ts
 
 | Graphs - DFS                                                 |          |        |
 | ------------------------------------------------------------ | -------- | ------ |

src/page-5/450. Delete Node in a BST/deleteNode.test.ts

@@ -0,0 +1,27 @@
+import { stringify } from 'flatted';
+
+import { generateBinaryTree } from '~/utils/binary-tree';
+
+import { deleteNode } from './deleteNode';
+
+describe('450. Delete Node in a BST', () => {
+  test('deleteNode', () => {
+    {
+      const root = generateBinaryTree([5, 3, 6, 2, 4, null, 7]);
+      const expected = generateBinaryTree([5, 4, 6, 2, null, null, 7]);
+      expect(stringify(deleteNode(root, 3))).toBe(stringify(expected));
+    }
+
+    {
+      const root = generateBinaryTree([5, 3, 6, 2, 4, null, 7]);
+      const expected = generateBinaryTree([5, 3, 6, 2, 4, null, 7]);
+      expect(stringify(deleteNode(root, 0))).toBe(stringify(expected));
+    }
+
+    {
+      const root = generateBinaryTree([]);
+      const expected = generateBinaryTree([]);
+      expect(stringify(deleteNode(root, 0))).toBe(stringify(expected));
+    }
+  });
+});

src/page-5/450. Delete Node in a BST/deleteNode.ts

@@ -0,0 +1,50 @@
+import type { TreeNode } from '~/utils/binary-tree';
+
+type DeleteNode = (root: TreeNode | null, key: number) => TreeNode | null;
+
+/**
+ * Accepted
+ */
+export const deleteNode: DeleteNode = (root, key) => {
+  // Base case: If the root is null, the tree is empty, or we've reached a leaf node.
+  if (root === null) return null;
+
+  // If the key to be deleted is less than the current node's value,
+  // search in the left subtree.
+  if (key < root.val) {
+    root.left = deleteNode(root.left, key);
+    return root; // Return the unchanged root after deletion in the left subtree.
+  }
+
+  // If the key to be deleted is greater than the current node's value,
+  // search in the right subtree.
+  if (key > root.val) {
+    root.right = deleteNode(root.right, key);
+    return root; // Return the unchanged root after deletion in the right subtree.
+  }
+
+  // If the key matches the current node's value, this is the node to be deleted.
+
+  // Case 1: Node has no left child, return the right child.
+  if (root.left === null) return root.right;
+
+  // Case 2: Node has no right child, return the left child.
+  if (root.right === null) return root.left;
+
+  // Case 3: Node has two children.
+  // Find the inorder successor (smallest node in the right subtree).
+  let minNode = root.right;
+
+  while (minNode.left !== null) {
+    minNode = minNode.left; // Traverse to the leftmost node.
+  }
+
+  // Replace the current node's value with the inorder successor's value.
+  root.val = minNode.val;
+
+  // Delete the inorder successor node (which is guaranteed to have at most one child).
+  root.right = deleteNode(root.right, minNode.val);
+
+  // Return the root of the updated tree.
+  return root;
+};