196th Commit

README.md

@@ -175,13 +175,14 @@ Ace Coding Interview with 75 Qs
 | 872. Leaf-Similar Trees                      | [Solution][872]  | Easy   |
 | 1448. Count Good Nodes in Binary Tree        | [Solution][1448] | Medium |
 | 437. Path Sum III                            | [Solution][437]  | Medium |
-| 1372. Longest ZigZag Path in a Binary Tree   | Solution         | Medium |
+| 1372. Longest ZigZag Path in a Binary Tree   | [Solution][1372] | Medium |
 | 236. Lowest Common Ancestor of a Binary Tree | Solution         | Medium |
 
 [104]: ./src/page-2/104.%20Maximum%20Depth%20of%20Binary%20Tree/maxDepth.ts
 [872]: ./src/page-9/872.%20Leaf-Similar%20Trees/leafSimilar.ts
 [1448]: ./src/page-14/1448.%20Count%20Good%20Nodes%20in%20Binary%20Tree/goodNodes.ts
 [437]: ./src/page-5/437.%20Path%20Sum%20III/pathSum.ts
+[1372]: ./src/page-13/1372.%20Longest%20ZigZag%20Path%20in%20a%20Binary%20Tree/longestZigZag.ts
 
 | Binary Tree - BFS                        |          |        |
 | ---------------------------------------- | -------- | ------ |

src/page-13/1372. Longest ZigZag Path in a Binary Tree/longestZigZag.test.ts

@@ -0,0 +1,23 @@
+import { generateBinaryTree } from '~/utils/binary-tree';
+
+import { longestZigZag } from './longestZigZag';
+
+describe('1372. Longest ZigZag Path in a Binary Tree', () => {
+  test('longestZigZag', () => {
+    {
+      // biome-ignore format: the array should not be formatted
+      const root = generateBinaryTree([1, null, 1, 1, 1, null, null, 1, 1, null, 1, null, null, null, 1]);
+      expect(longestZigZag(root)).toBe(3);
+    }
+
+    {
+      const root = generateBinaryTree([1, 1, 1, null, 1, null, null, 1, 1, null, 1]);
+      expect(longestZigZag(root)).toBe(4);
+    }
+
+    {
+      const root = generateBinaryTree([1]);
+      expect(longestZigZag(root)).toBe(0);
+    }
+  });
+});

src/page-13/1372. Longest ZigZag Path in a Binary Tree/longestZigZag.ts

@@ -0,0 +1,36 @@
+import type { TreeNode } from '~/utils/binary-tree';
+
+type LongestZigZag = (root: TreeNode | null) => number;
+
+/**
+ * Accepted
+ */
+export const longestZigZag: LongestZigZag = (root) => {
+  let maxLength = 0;
+
+  function dfs(node: TreeNode | null, direction: 'left' | 'right', length: number): void {
+    if (!node) return;
+
+    // Update the maximum ZigZag length
+    maxLength = Math.max(maxLength, length);
+
+    // If the current direction is 'left', try to go left and then right
+    if (direction === 'left') {
+      dfs(node.left, 'right', length + 1);
+      dfs(node.right, 'left', 1);
+    }
+    // If the current direction is 'right', try to go right and then left
+    else {
+      dfs(node.right, 'left', length + 1);
+      dfs(node.left, 'right', 1);
+    }
+  }
+
+  // Start DFS from the root, considering both initial directions
+  if (root) {
+    dfs(root.left, 'right', 1);
+    dfs(root.right, 'left', 1);
+  }
+
+  return maxLength;
+};