Sync LeetCode submission Runtime - 0 ms (100.00%), Memory - 17.8 MB (5.01%)

Author: jimit105

0314-binary-tree-vertical-order-traversal/README.md

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+<p>Given the <code>root</code> of a binary tree, return <em><strong>the vertical order traversal</strong> of its nodes&#39; values</em>. (i.e., from top to bottom, column by column).</p>
+
+<p>If two nodes are in the same row and column, the order should be from <strong>left to right</strong>.</p>
+
+<p>&nbsp;</p>
+<p><strong class="example">Example 1:</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2024/09/23/image1.png" style="width: 400px; height: 273px;" />
+<pre>
+<strong>Input:</strong> root = [3,9,20,null,null,15,7]
+<strong>Output:</strong> [[9],[3,15],[20],[7]]
+</pre>
+
+<p><strong class="example">Example 2:</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2024/09/23/image3.png" style="width: 450px; height: 285px;" />
+<pre>
+<strong>Input:</strong> root = [3,9,8,4,0,1,7]
+<strong>Output:</strong> [[4],[9],[3,0,1],[8],[7]]
+</pre>
+
+<p><strong class="example">Example 3:</strong></p>
+<img alt="" src="https://assets.leetcode.com/uploads/2024/09/23/image2.png" style="width: 350px; height: 342px;" />
+<pre>
+<strong>Input:</strong> root = [1,2,3,4,10,9,11,null,5,null,null,null,null,null,null,null,6]
+<strong>Output:</strong> [[4],[2,5],[1,10,9,6],[3],[11]]
+</pre>
+
+<p>&nbsp;</p>
+<p><strong>Constraints:</strong></p>
+
+<ul>
+	<li>The number of nodes in the tree is in the range <code>[0, 100]</code>.</li>
+	<li><code>-100 &lt;= Node.val &lt;= 100</code></li>
+</ul>

0314-binary-tree-vertical-order-traversal/solution.py

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+# Approach 2: BFS without sorting
+
+# Time: O(n)
+# Space: O(n)
+
+# Definition for a binary tree node.
+# class TreeNode:
+#     def __init__(self, val=0, left=None, right=None):
+#         self.val = val
+#         self.left = left
+#         self.right = right
+
+from collections import defaultdict, deque
+
+class Solution:
+    def verticalOrder(self, root: Optional[TreeNode]) -> List[List[int]]:
+        if not root:
+            return []
+
+        columnTable = defaultdict(list)
+        min_column = max_column = 0
+        queue = deque([(root, 0)])
+
+        while queue:
+            node, column = queue.popleft()
+
+            if node is not None:
+                columnTable[column].append(node.val)
+                min_column = min(min_column, column)
+                max_column = max(max_column, column)
+
+                queue.append([node.left, column - 1])
+                queue.append([node.right, column + 1])
+
+        return [columnTable[x] for x in range(min_column, max_column + 1)]
+