Binary Tree Visualizers

29

Step through every Binary Tree problem with animated runtime state, source highlighting, and curated test cases. Built for coding-interview prep and durable algorithmic intuition.

Balanced Binary Tree

Bottom-up DFS checking if subtree heights differ by at most 1. Early termination on imbalance.

Binary Tree Inorder Traversal

Recursive DFS visiting left, then root, then right. See how in-order produces sorted output for BSTs.

Binary Tree Inorder Traversal - Iterative

Iterative inorder using curr pointer + stack. Two-phase loop: go left (push), then pop-record-go right.

Iterative Stack

Binary Tree Level Order Traversal

BFS level-order traversal using a queue. Watch nodes get visited level by level with queue state tracked in real time.

Binary Tree Level Order Traversal - Recursion

DFS recursion with a level parameter to slot each node into the correct sub-array — no queue needed.

DFS with Level Parameter

Binary Tree Maximum Path Sum

Postorder DFS computing max gain from each subtree while tracking the global maximum path sum.

Binary Tree Postorder Traversal

Recursive DFS visiting left, then right, then root. Children are always processed before their parent.

Binary Tree Postorder Traversal - One Stack

Iterative postorder with a single stack. Uses curr and lastVisited pointers to avoid revisiting the right subtree.

Iterative Stack

Binary Tree Postorder Traversal - Two Stacks

Iterative postorder using two stacks. Phase 1: fill stack2 in reverse-postorder via stack1. Phase 2: pop stack2 for correct order.

Iterative Stack

Binary Tree Preorder Traversal

Recursive DFS visiting root, then left, then right. Watch the call stack and result array build in real time.

Binary Tree Preorder Traversal - Iterative

Iterative DFS using an explicit stack. Push root, then loop: pop → record → push right → push left.

Iterative Stack

Binary Tree Right Side View

BFS collecting the last node of each level. See which nodes are visible from the right side of the tree.

Binary Tree Zigzag Level Order Traversal

BFS with alternating direction per level. Watch the zigzag pattern build as levels alternate left-to-right and right-to-left.

Construct Binary Tree from Preorder and Inorder Traversal

Given preorder and inorder arrays, recursively construct a binary tree. Preorder gives the root, while inorder splits left and right subtrees.

Trees / Recursion

Count Good Nodes in Binary Tree

DFS tracking the max value on the path from root. A node is good if its value >= max so far.

Diameter of Binary Tree

DFS computing height while tracking max left+right height across all nodes to find the longest path.

Invert Binary Tree

Recursive DFS swapping left and right children at every node. Watch the tree mirror itself.

Lowest Common Ancestor of a Binary Tree

DFS returning p or q when found, identifying the LCA where both subtrees return non-null.

Maximum Depth of Binary Tree

DFS recursion computing 1 + max(left, right) depth. Watch depth values propagate back up the tree.

Maximum Depth of Binary Tree - Top Down

Top-down DFS carrying depth as a parameter. Update global max at each node — preorder style.

DFS exploring root-to-leaf paths with a running sum. Backtrack when a path doesn't reach the target.

Path Sum - Top Down

Top-down DFS carrying a running sum. Check newSum === target at leaves. An 'ans' flag locks in the result.

Populating Next Right Pointers in Each Node

BFS level-by-level connecting each node's next pointer to the next node in the same level.

Recursive DFS comparing two trees node by node. Both structure and values must match.

Serialize and Deserialize Binary Tree

Convert a binary tree to a string using level-order traversal (BFS), and reconstruct the exact same tree from the string.

Subtree of Another Tree

For each node in the main tree, check if the subtree rooted there matches the target tree.

Subtree of Another Tree (Serialization)

Pre-order serialize both trees with null markers, then check if subRoot's string is a substring of root's string.

Binary Tree / Serialization

Recursive mirror check comparing left.left with right.right and left.right with right.left.

Symmetric Tree - Iterative

Iterative BFS using a queue: enqueue mirror pairs, dequeue two at a time, validate, and push children in mirror order.