Create diameterOfBinaryTree.test.js

Author: RinkiJhunjhunwala

Trees/test/diameterOfBinaryTree.test.js

@@ -0,0 +1,47 @@
+import { diameterOfBinaryTree } from './diameterOfBinaryTree';
+import { TreeNode } from '../utils/TreeNode';
+
+describe('Diameter of a Binary Tree', () => {
+  it('should calculate the correct diameter for a standard tree', () => {
+    //      1
+    //     / \
+    //    2   3
+    //   / \
+    //  4   5
+    // Longest path is 4 -> 2 -> 1 -> 3 (length 3) or 5 -> 2 -> 1 -> 3 (length 3)
+    const root = new TreeNode(1);
+    root.left = new TreeNode(2);
+    root.right = new TreeNode(3);
+    root.left.left = new TreeNode(4);
+    root.left.right = new TreeNode(5);
+    expect(diameterOfBinaryTree(root)).toBe(3);
+  });
+
+  it('should work for a skewed tree where diameter does not pass through root', () => {
+    //      1
+    //     /
+    //    2
+    //   / \
+    //  3   4
+    //     / \
+    //    5   6
+    //   /     \
+    //  7       8
+    // Longest path is 7 -> 5 -> 4 -> 6 -> 8 (length 4)
+    const root = new TreeNode(1);
+    root.left = new TreeNode(2);
+    root.left.left = new TreeNode(3);
+    root.left.right = new TreeNode(4);
+    root.left.right.left = new TreeNode(5);
+    root.left.right.right = new TreeNode(6);
+    root.left.right.left.left = new TreeNode(7);
+    root.left.right.right.right = new TreeNode(8);
+    expect(diameterOfBinaryTree(root)).toBe(6);
+  });
+
+  it('should return 0 for a null or single-node tree', () => {
+    expect(diameterOfBinaryTree(null)).toBe(0);
+    const singleNode = new TreeNode(1);
+    expect(diameterOfBinaryTree(singleNode)).toBe(0);
+  });
+});