21. Build Tree from Postorder + Inorder
Reconstructs binary tree using Postorder[-1] as root and Inorder to divide left/right subtrees.
Live loop — open the studio to scrub, add your own array, or race it in Battle Arena.
Asked in interviews at
Reference implementation (Python)
def build_tree_post_in(inorder, postorder):
if not inorder or not postorder: return None
root_val = postorder.pop()
root = TreeNode(root_val)
mid = inorder.index(root_val)
root.right = build_tree_post_in(inorder[mid+1:], postorder)
root.left = build_tree_post_in(inorder[:mid], postorder)
return rootEmbed this visualization
Drop a live, looping 21. Build Tree from Postorder + Inorder canvas into a blog post or course page.
<iframe src="/embed/build-tree-post-in" width="100%" height="380" style="border:1px solid #e6e8ec;border-radius:14px" loading="lazy" title="3D algorithm visualization by CodeWithMunnaX"></iframe>Frequently asked
What is the time and space complexity of 21. Build Tree from Postorder + Inorder?
21. Build Tree from Postorder + Inorder runs in O(n) time and O(n) auxiliary space.
Is the 21. Build Tree from Postorder + Inorder visualizer free?
The core 3D visualizer, Web Audio chimes and step intuition are free. A one-time ₹49 Pro Pass unlocks advanced algorithms, large custom arrays, Battle Arena and reel export.
Which companies ask 21. Build Tree from Postorder + Inorder in interviews?
21. Build Tree from Postorder + Inorder shows up in interviews at Netflix, Amazon, ByteDance.
How does the 3D visualization of 21. Build Tree from Postorder + Inorder work?
Each array value becomes a 3D pillar whose height maps to its value. Comparisons glow amber, swaps flash red, and settled elements lock green while a floating pointer badge tracks the active index — synchronized line-by-line with the Python code.