Zigzag Level Order Traversal — BFS with Deque in Python
Zigzag level order traversal of a binary tree using BFS and deque. Step-by-step Python solution with visual trace, complexity analysis, and interview tips.
·5 min read · #dsa#queues#trees
#trees
33 posts · page 1 of 1
Flatten Binary Tree to Linked List
Learn how to flatten a binary tree to a linked list using preorder threading, Morris traversal, and how to convert a BST to a sorted doubly linked list — with full Python implementations and Big-O analysis.
·9 min read · #dsa#trees#intermediate
BST Iterator, Range Queries, and Closest Value
Master BST iterator using stack-based controlled in-order traversal, range sum queries, counting nodes in range, closest value, and closest K values — with full Python implementations.
·11 min read · #dsa#trees#intermediate
Boundary Traversal of Binary Tree
Complete guide to boundary traversal — left boundary, leaf nodes, and right boundary in reverse. Multiple Python approaches with edge case handling.
·8 min read · #dsa#trees#intermediate
Distance Problems in Binary Trees
Solve distance problems in binary trees — distance between two nodes, all nodes at distance K, burning a tree from a node, and sum of distances using rerooting. Full Python implementations.
·12 min read · #dsa#trees#intermediate
Binary Tree Interview Patterns: Complete Guide
The complete guide to binary tree interview patterns — top 20 patterns, DFS vs BFS decision guide, recursive vs iterative approaches, common mistakes, complexity cheatsheet, and template code.
·14 min read · #dsa#trees#interviews
Tree Pruning and Deletion Patterns
Master tree pruning and deletion — delete nodes in BST, prune binary trees, trim BST to range, and remove leaves with a given value. Full Python implementations with Big-O analysis.
·10 min read · #dsa#trees#intermediate
Path Sum Problems: All Variants Explained
Solve all Path Sum variants — root-to-leaf existence, find all paths, any-to-any with prefix sums. Complete Python solutions with Big-O analysis.
·11 min read · #dsa#trees#intermediate
Symmetric Tree, Same Tree, and Subtree Problems
Check if a tree is symmetric, whether one tree is a subtree of another, same tree comparison, and flip equivalence. Python solutions with analysis.
·9 min read · #dsa#trees#intermediate
Vertical Order Traversal of Binary Tree
Master vertical order traversal with column-based grouping. Includes top view, bottom view, and vertical sum with Python solutions.
·9 min read · #dsa#trees#intermediate
Binary Tree Zigzag Level Order Traversal
Master zigzag level-order traversal of binary trees using deque and flag toggling. Multiple Python approaches with step-by-step walkthrough.
·8 min read · #dsa#trees#intermediate
AVL Tree Rotations: Self-Balancing BST Explained
Understand AVL trees — balance factors, all four rotation types (LL, RR, LR, RL), insertion with rebalancing, and complete Python implementation with height tracking.
·10 min read · #dsa#trees#intermediate
Building a Balanced BST from Sorted Data
Convert sorted arrays and linked lists into balanced BSTs using divide and conquer. BST to sorted DLL, Day-Stout-Warren algorithm, and Python implementations.
·11 min read · #dsa#trees#intermediate
Binary Lifting for LCA and Kth Ancestor Queries
Master binary lifting to answer Lowest Common Ancestor (LCA) and kth ancestor queries in O(log n) with O(n log n) preprocessing. Full Python implementations with tree examples.
·11 min read · #dsa#trees#advanced
Binary Tree Views: Left, Right, Top & Bottom
Solve all binary tree view problems — left view, right view, top view, bottom view, and vertical order traversal. BFS-based Python implementations.
·10 min read · #dsa#trees#intermediate
BST Operations Deep Dive: Insert, Delete & Search
Master Binary Search Tree operations — insert, search, and all three delete cases with in-order successor. Full Python implementation with time complexity analysis.
·10 min read · #dsa#trees#intermediate
Lowest Common Ancestor: BST, Binary Tree & Binary Lifting
Master LCA problems — recursive DFS for binary trees, BST property shortcut, parent pointers, and binary lifting for O(log n) queries. Full Python code.
·11 min read · #dsa#trees#intermediate
N-ary Trees and Trie Applications
Master N-ary tree traversals and Trie data structure — autocomplete, spell check, word dictionary, wildcard search. Complete Python implementations.
·11 min read · #dsa#trees#intermediate
Red-Black Trees Explained: Rules, Rotations & Real-World Usage
Understand Red-Black trees — the 5 rules, insertion cases, color flips, rotations, comparison with AVL, and why Java TreeMap and Linux use them.
·11 min read · #dsa#trees#advanced
Constructing Binary Trees from Traversal Sequences
Build binary trees from inorder + preorder, inorder + postorder, and preorder + postorder. Hashmap optimization, edge cases, and Python recursive solutions.
·10 min read · #dsa#trees#intermediate
Tree Diameter and Path Problems
Find the diameter of a binary tree using DFS, solve maximum path sum, and understand the two-BFS approach for general trees. Full Python implementations.
·9 min read · #dsa#trees#intermediate
Tree Serialization and Deserialization
Serialize binary trees to strings and deserialize them back. BFS and DFS approaches with null handling, Python implementations, and real-world uses.
·9 min read · #dsa#trees#intermediate
Advanced Tree Algorithms: HLD, Centroid & Euler Tour
Deep dive into advanced tree algorithms — heavy-light decomposition, Euler tour technique, centroid decomposition, LCA with binary lifting, tree DP with rerooting, and virtual trees.
·11 min read · #dsa#trees#advanced
Tree Traversal Patterns: Inorder, Preorder, Postorder, Level-Order, and Morris
Master every tree traversal method with recursive, iterative, and Morris traversal implementations, plus classic LeetCode tree problems.
·7 min read · #leetcode#trees#traversal
Binary Tree Level Order Traversal — Queue Size Snapshot
The queue-with-size BFS pattern, why DFS still works, and how this template extends to zigzag and right-side view.
·5 min read · #dsa#leetcode#trees
Kth Smallest Element in a BST — Iterative Inorder Early Exit
The inorder traversal trick, the iterative early-exit version, and the follow-up that haunts FAANG interviews.
·5 min read · #dsa#leetcode#trees
Lowest Common Ancestor of a BST — One-Line Guided Walk
Why BST ordering collapses LCA into a one-line traversal, and the iterative version that needs zero extra space.
·5 min read · #dsa#leetcode#trees
Path Sum — DFS With a Running Target
The DFS-with-decrement trick, why the leaf condition is the whole problem, and the variants that build on it.
·5 min read · #dsa#leetcode#trees
Serialize and Deserialize Binary Tree — Preorder With Null Sentinels
The preorder-with-nulls encoding, the iterator-driven decoder, and why level-order is a worse choice than it looks.
·6 min read · #dsa#leetcode#trees
Validate Binary Search Tree — Min/Max Bounds DFS
The seductive wrong answer, the correct min/max bounds approach, and how to defend it in an interview.
·5 min read · #dsa#leetcode#trees
Binary Trees in DSA: Introduction
A practical introduction to binary trees — the TreeNode class, terminology (full, complete, perfect, balanced), height vs depth, BSTs, and the small calculations you need to reason about tree problems.
·9 min read · #dsa#trees#beginners
Binary Tree Traversals: Inorder, Preorder, Postorder, Level-Order
A practical guide to the four canonical binary tree traversals — recursive and iterative versions, when to use each, and the patterns that make them click.
·7 min read · #dsa#trees#intermediate
Binary Trees: 8 Practice Problems with Solutions
Eight classic binary tree interview problems with examples, approach notes, and clean Python solutions — max depth, same tree, invert, symmetric, path sum, LCA, validate BST, and serialize/deserialize.
·9 min read · #dsa#trees#practice