Limit tree height by deleting nodesCodingYou are given a rooted N-ary tree. Every node has a unique integer id. The tree is passed as children: dictint, listint (a node with no entry has no children) together with the…
Last asked Oct 2026
#dfs
+4Mini spreadsheet with formulas and cycle detectionCodingBuild a mini spreadsheet with cell get and set, formula evaluation over dependencies, cached values with eager updates, and cycle detection. Covers the bank's spreadsheet variants…Last asked Oct 2026
+1Lowest common manager in an org chartCodingA company's reporting structure is a rooted tree. Each person is an Employee with a unique name and a list reports of the people who report to them directly. The root is the CEO…Last asked Oct 2026
+3Word search with a word search II follow-upCodingFind words on a letter grid by adjacent moves, then extend the solution to finding many words at once efficiently. Reported on 1point3acres' Glean bank; reconstructed in our own…Last asked Sep 2026- +4Number of islandsCodingGiven a binary matrix, return how many islands it has: groups of 1 cells connected up, down, left or right (diagonals don't connect).Last asked Sep 2026
+1Unix find command with pluggable filtersCodingImplement a small version of the Unix find command over an in-memory file system. The file system holds directories and files. Each file has a name and a size in bytes. Its…Last asked Sep 2026
Exchange rate between two currencies through chained conversionsCodingYou get a list of rates from, to, rate, each meaning one unit of from is worth rate units of to. Given a source and a target currency, return the rate between them by chaining…Last asked Sep 2026
Minimum-cost encryption of a directory treeCodingA storage service keeps a filesystem as a tree: Compliance requires every file in the tree to end up encrypted. You can issue two kinds of calls: - encrypt(filepath)Last asked Sep 2026
Drive to an unseen destination without going in circlesCodingA car must reach a destination on a map it cannot see in advance. Each time it arrives at a place, it learns which directions it can continue in from there. Write the search that…Last asked Sep 2026- Throne inheritance without an initial kingCodingModel a royal family's line of succession: people are born to parents, people die, and you return the current order of inheritance (a pre-order walk of the family tree that skips…Last asked Sep 2026
Parse HTML into an element tree and query itCodingYou are asked to "write an HTML parser" with no definition of the input, the output or the edge cases. Part of the exercise is pinning that down: ask for examples, then write down…Last asked Aug 2026- Arrange crops into connected regions of a gardenCodingA rectangular garden has N rows and M columns, and there are K crop types. Crop i must take exactly counti cells, and the counts add up to N M. Return any planting that uses every…Last asked Aug 2026
Collect the characters along a path in a gridCodingA 2D grid has one path that starts at (0, 0); path cells hold either or a letter, and other cells are empty. Follow the path and return the letters on it, in order, as a string…Last asked Aug 2026
Print each tree node's level and whether it is balancedCodingGiven a tree, walk it with a depth-first search and report, for every node, its level and whether the subtree under it is balanced (by the definition the interviewer gives, such…Last asked Aug 2026- Count simple paths whose labels match a prefixCodingEvery node of a graph carries a label. Count the simple paths (paths that never repeat a node) whose sequence of labels matches a given prefix string. Explain how you prune the…Last asked Aug 2026
Sum root-to-leaf numbersCodingEach node of a binary tree holds a digit, so every root-to-leaf path spells a number. Return the sum of all those numbers.Last asked Aug 2026- Is there an island of exactly size k?CodingGiven a grid of land and water, answer many queries of the form "is there an island of exactly k cells?". Find the islands once, then answer each query quickly, and discuss what…Last asked Aug 2026
- +1Minimum root-to-leaf path sumCodingGiven the root of a binary tree whose nodes hold integers (values may be negative), find the root-to-leaf path with the smallest sum. A leaf is a node with no children. A…Last asked Aug 2026
- Players whose rank is fixed by game resultsCodingThere are n players, numbered 0 to n - 1, and a list of game results where a pair (u, v) means player u beat player v. Assume the results come from one strict ranking, so there…Last asked Aug 2026
Inherited permissions across teams, folders and filesCodingDesign a permission system for a workspace organized as a hierarchy of teams, folders, and files. - A team is a root. It can contain folders and files. - A folder sits inside a…Last asked Jul 2026- Boundary of a binary treeCodingWalk around the outside of a binary tree starting at the root: down the left edge, along the leaves from left to right, then up the right edge. The nodes you pass form the…Last asked Jul 2026
Count connected friend groupsCodingGiven people and the friendships between them, count the friend groups: two people are in the same group when they are friends, directly or through a chain of friends. Solve it…Last asked Jul 2026- Shortest bridge between two islandsCodingA binary grid contains exactly two islands of 1s (4-directionally connected). Return the fewest 0 cells you must flip to 1 to connect them. Find one island with DFS, then expand…Last asked Jun 2026
- Team with the highest average salary in an org chartCodingGiven an org chart where every employee has a salary, find the manager whose team (the manager and everyone below them) has the highest average salary.Last asked Jun 2026
- Longest path of equal-valued tree nodesCodingGiven a binary tree, return the length of the longest path in which every node has the same value. The path may pass through any node and need not include the root; agree with the…Last asked Jun 2026
Palindromic paths from a node to the rootCodingA storage system keeps its directories in a tree. Each directory holds one lowercase letter as a label. You are given: - arr: a list of n lowercase letters; arri is the label of…Last asked May 2026- Count connected components in an undirected graphCodingGiven n nodes and a list of undirected edges, return the number of connected components. It was also asked with products: each pair says two products are in the same category, and…Last asked May 2026
- Does a word exist as a path in a graph?CodingEvery node of a graph holds a letter. Decide whether a word can be spelled by walking along edges, one letter per node. Agree on whether a node may be used twice, and give the…Last asked May 2026
- Longest consecutive sequence path in a binary treeCodingReturn the length of the longest parent-to-child path in a binary tree in which each value is exactly one more than the value before it. Follow-up: the path may go in any…Last asked Apr 2026
- Longest water-flow path with momentumCodingYou get an m x n matrix of heights. Water starts at any cell and moves to a neighboring cell up, down, left or right. Whether it may move on depends on the heights and on the…Last asked Apr 2026
- +1Binary tree right side viewCodingReturn the values visible when you look at a binary tree from the right: the last node of each level, top to bottom. Follow-ups: the left side view, and both views in a single…Last asked Apr 2026
- Longest increasing path in a matrixCodingReturn the length of the longest path in an integer matrix that moves up, down, left or right and only to strictly larger values. Use memoised DFS (or a topological order) so…Last asked Apr 2026
- Count islands with diagonal connectivityCodingCount the islands in a grid of land and water where land cells are joined in all eight directions, diagonals included.Last asked Apr 2026
- Detonate the most bombs in a chain reactionCodingEach bomb has a position and a blast radius. Setting one off detonates every bomb within its radius, and those set off others in turn. Return the largest number of bombs that can…Last asked Apr 2026
- +1Serialize and deserialize a binary treeCodingTurn a binary tree into a string and rebuild the identical tree from that string. Choose a format (pre-order with null markers, or level order), handle empty trees and negative…Last asked Apr 2026
- +1Max area of islandCodingGiven a binary matrix, return the area of the largest island: a group of 1 cells connected up, down, left or right (diagonals don't connect).Last asked Mar 2026
List every file path in a directory treeCodingGiven a directory tree (folders containing files and other folders), return the full path of every file. Write it with a depth-first search, then discuss an iterative version and…Last asked Mar 2026- Cheapest common ancestor in a treeCodingNodes of a tree carry costs. Given a set of nodes, find the common ancestor of all of them that has the lowest cost.Last asked Feb 2026
- Build, validate and prune a computation graphCodingImplement a small graph of neural-network operations: add nodes and dependencies, check structural rules, detect cycles, and remove branches that do not contribute to the required…Last asked Feb 2026
- Nested list weight sumCodingA nested list holds integers and other nested lists. Return the sum of every integer multiplied by its depth (integers in the outer list have depth 1).Last asked Feb 2026
+2Minimum distance between two nodes in an N-ary treeCodingYou are given the root of an N-ary tree. Every node has an integer val, unique within the tree, and a list children of its direct children. There are no parent pointers…Last asked Feb 2026- Shortest path between two cells in a gridCodingGiven a grid with open and blocked cells, return the length of the shortest path from a start cell to a target cell moving up, down, left and right. A follow-up changes the…Last asked Feb 2026
- Check that a parent array forms a valid treeCodingYou get an array where parenti is the parent of node i (the root has no parent, for example -1). Return whether the array describes one valid tree: exactly one root, no cycles…Last asked Feb 2026
Maximum path sum in an N-ary treeCodingEach node of an N-ary tree holds an integer. A path joins any two nodes through parent and child links and visits each node at most once. Return the largest path sum. Unlike the…Last asked Jan 2026- Build order for a package and its dependenciesCodinggetdependencies(package) returns a package's direct dependencies; the whole graph is not given up front. Given a target package, return an order in which to build it and…Last asked Jan 2026
- Flood fillCodingGiven an image as a grid of colors, a starting pixel and a new color, recolor the starting pixel and every pixel connected to it (up, down, left, right) that has the same original…Last asked Jan 2026
- All root-to-leaf path sumsCodingReturn a list with the sum of the values along every root-to-leaf path of a binary tree, one entry per leaf, in left-to-right order.Last asked Dec 2025
- Making a large islandCodingIn a binary grid you may change at most one water cell to land. Return the size of the largest island you can end up with. Label each island and its size once, then try each water…Last asked Dec 2025
- +1Detect a cycle in a directed graphCodingDecide whether a directed graph contains a cycle, using depth-first search with node states or Kahn's topological sort. Variants that came up: start with a linked list (fast and…Last asked Dec 2025
- Lowest common ancestor in an N-ary treeCodingGiven the root of an N-ary tree and two of its nodes, return their lowest common ancestor. Use one depth-first pass in which each subtree reports whether it contains each of the…Last asked Dec 2025
- Mode of a ternary search treeCodingIn this tree each node has up to three children: the left subtree holds smaller values, the middle child equals the node's value, and the right subtree holds larger values. Return…Last asked Nov 2025
- Find a target in an unknown grid with a robot APICodingA robot sits somewhere in a grid you cannot see: you don't know its size, its walls or where you start. You can only call the robot's API: move forward (which reports whether it…Last asked Nov 2025
- Longest increasing downward path in a binary treeCodingIn a binary tree, find the longest path that goes from a node down to one of its descendants where every child's value is greater than its parent's (not necessarily by exactly…Last asked Nov 2025
- Cells water reaches flowing downhillCodingA 2D map gives the height of each cell. A drop of water lands on one cell and flows to neighbouring cells (up, down, left, right) whose height is not greater than the cell it is…Last asked Oct 2025
- Range sum of a BSTCodingGiven the root of a binary search tree and a range low, high, return the sum of the values inside the range, skipping subtrees that cannot contain any. Variants reported: return…Last asked Oct 2025
- Fill a second tree with subtree sums of the firstCodingYou get the roots of two complete binary trees with exactly the same shape. For every node of the second tree, set its value to the sum of the subtree rooted at the matching node…Last asked Sep 2025
- Check that each tree node equals its subtree's averageCodingFor a binary tree, decide whether every node's value equals the average of the values in its subtree (or of the nodes below it, as the interviewer defines it), or count the nodes…Last asked Sep 2025
- +1Left and right views of a binary treeCodingReturn the left view of a binary tree (the first node seen at each level from the left) and the right view (the last node at each level). Write it with breadth-first search, then…Last asked Sep 2025
- Root-started value path in an N-ary treeCodingYou are given the root of an N-ary tree (each node has an integer val and a list of children) and a list of integers path. Return true if there is a downward path that starts at…Last asked Sep 2025
- Course schedule: detect a cycle and return an orderCodingCourses have prerequisites. Decide whether all courses can be finished (the prerequisite graph has no cycle), and if so return a valid order to take them. Use depth-first search…Last asked Sep 2025
- Shortest path in an unweighted graph: BFS versus DFSCodingExplain how to find the shortest path between two nodes of an unweighted graph and its time complexity, without necessarily writing code. Then compare: why breadth-first search…Last asked Sep 2025
- Group movies by graph traversalCodingMovies are linked to each other (for example by shared attributes or similarity pairs). Put every movie into its group, where a group is a set of movies connected through links…Last asked Sep 2025
- Lock, unlock and upgrade nodes in a treeCodingA tree is given by a parent array. Implement lock(node, user), unlock(node, user) and upgrade(node, user): a node can be locked by a user if it is unlocked; unlocked only by the…Last asked Aug 2025
- Flatten a binary tree to a linked listCodingFlatten a binary tree in place into a chain that follows pre-order, using the right pointers as next and setting every left pointer to null.Last asked Aug 2025
- Robot room cleanerCodingA cleaning robot is placed in an unknown room with obstacles. Using only move(), turnLeft(), turnRight() and clean(), clean every reachable cell. Explore by depth-first search…Last asked Aug 2025
- Shortest bridgeCodingA grid holds exactly two islands. Return the fewest water cells to flip to connect them: mark one island with depth-first search, then expand from all its cells with breadth-first…Last asked Jul 2025
- Same-value region from a start pixel, and its borderCodingAn image is a grid of 0s and 1s. From a starting pixel, find every connected pixel with the same value. Follow-up: return the region's border, the neighbouring pixels that are not…Last asked Jul 2025
Shipping route cost pathsCodingA parcel carrier publishes its shipping routes as a list of strings. Each string has the form source:target:method:cost: - source and target are country codes. A route ships one…- Peel an N-ary tree one leaf layer per dayCodingEvery day, all leaves of an N-ary tree fall off at the same time. A leaf is a node with no children left. When a node loses its last child, it becomes a leaf and falls on the next…
Minimum starting vertices to reach a cyclic directed graphCodingYou are given a directed graph with n vertices labeled 0 to n - 1 and a list edges, where edgesi = u, v is a directed edge from u to v. The graph may contain cycles, self-loops…
Merge two n-ary trees by child positionCodingImplement mergetrees(root1, root2). It takes the roots of two n-ary trees and returns the root of a new tree that merges them. Each node has an integer val and an ordered list…- Maximum path sum between two leaves of a binary treeCodingYou are given the root of a binary tree. Every node stores an integer, which may be negative. A leaf is a node with no children. A leaf-to-leaf path starts at one leaf, moves…
- +1Root of the largest tree in a forestCodingYou are given a list relations. Each entry child, parent says that parent is the direct parent of child. Together the relations form a forest: there are no cycles, and every node…
- +2Compress an n-ary tree by promoting childrenCodingEach node of an n-ary tree holds a unique integer value and an ordered list of children. You are given the root and a list compressednodes of values. Implement compress(root…