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LeetCode 1059: All Paths from Source Lead to Destination

Problem Restatement We are given a directed graph with n nodes, a source node, and a destination node. Return true if and only if all paths from source lead to destination . This requires: Every path from source eventually reaches destination . destination has no outgoing edges (it is a terminal node on all paths). The official constraints state that 1 <= n <= 10^4 and 0 <= edges.length <=...

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LeetCode 1042: Flower Planting With No Adjacent

Problem Restatement We have n gardens labeled 1 to n and paths between some gardens. Each garden must be assigned one of 4 flower types ( 1 to 4 ). No two adjacent gardens (connected by a path) can have the same flower type. Since each node has at most 3 neighbors (guaranteed by the problem), a valid assignment always exists. Return a valid assignment as an array answer where...

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LeetCode 847: Shortest Path Visiting All Nodes

Problem Restatement We are given an undirected connected graph with n nodes labeled from 0 to n - 1 . The graph is given as an adjacency list: graph[i] contains all nodes directly connected to node i . We need to return the length of the shortest path that visits every node at least once. Important details: Rule Meaning Start We may start at any node End We may stop...

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LeetCode 924: Minimize Malware Spread

Problem Restatement We are given an undirected graph with n nodes. The graph is represented by an adjacency matrix: graph[i][j] == 1 means node i is directly connected to node j . Some nodes are initially infected with malware. These nodes are listed in: initial Malware spreads through connected edges. If one node in a connected component is infected, eventually every node in that component becomes infected. We must remove...

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LeetCode 997: Find the Town Judge

Problem Restatement There are n people in a town labeled from 1 to n . We are given an array trust , where each pair: [a, b] means person a trusts person b . We need to find the town judge. If the judge exists, then: Rule Meaning Trusts nobody The judge has no outgoing trust Trusted by everyone else Exactly n - 1 people trust the judge Unique There...

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LeetCode 841: Keys and Rooms

Problem Restatement We are given n rooms numbered from 0 to n - 1 . All rooms are locked except room 0 . Each room contains keys. A key is represented by an integer, and key x unlocks room x . When we enter a room, we can take all keys inside it. Return True if we can visit every room. Otherwise, return False . Input and Output Item Meaning...

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LeetCode 947: Most Stones Removed with Same Row or Column

Problem Restatement We are given stones on a 2D plane. Each stone has coordinates: [x, y] A stone can be removed if there is another stone still on the plane that shares either: same row same column Return the maximum number of stones that can be removed. The official statement asks for the largest possible number of removable stones, where each coordinate contains at most one stone. Input and Output...

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LeetCode 996: Number of Squareful Arrays

Problem Restatement We are given an integer array nums . An array is squareful if the sum of every pair of adjacent elements is a perfect square. We need to return the number of unique permutations of nums that are squareful. For example, if two adjacent values are 1 and 8 , then: 1 + 8 = 9 Since 9 is a perfect square, this adjacent pair is valid. The...

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LeetCode 839: Similar String Groups

Problem Restatement We are given an array of strings strs . Every string is an anagram of every other string in the array, and all strings have the same length. Two strings are similar if either: They are already equal. We can make them equal by swapping at most two letters in one of the strings. We need to return the number of similar string groups. Similarity is transitive for...

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LeetCode 994: Rotting Oranges

Problem Restatement We are given an m x n grid. Each cell can have one of three values: Value Meaning 0 Empty cell 1 Fresh orange 2 Rotten orange Every minute, any fresh orange that is 4-directionally adjacent to a rotten orange becomes rotten. The four directions are: up, down, left, right Diagonal cells do not count. We need to return the minimum number of minutes needed until no fresh...

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LeetCode 773: Sliding Puzzle

Problem Restatement We are given a 2 x 3 sliding puzzle board. The board contains the numbers 1 through 5 and one empty slot represented by 0 . A move consists of swapping 0 with one of its 4-directionally adjacent numbers. The goal state is: [[1, 2, 3], [4, 5, 0]] Return the least number of moves needed to reach the goal state. If it is impossible, return -1 ....

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LeetCode 797: All Paths From Source to Target

Problem Restatement We are given a directed acyclic graph, also called a DAG. The graph has n nodes labeled: 0, 1, 2, ..., n - 1 The graph is represented as an adjacency list. graph[i] contains every node we can visit directly from node i . We need to return all possible paths from node 0 to node n - 1 , in any order. The graph is guaranteed to...

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LeetCode 943: Find the Shortest Superstring

Problem Restatement We are given an array of strings: words We need to return the shortest string that contains every string in words as a substring. If several shortest answers exist, we may return any of them. The problem also says that no string in words is a substring of another string in words . This lets us focus on ordering and overlapping the strings, instead of removing already-contained strings....

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LeetCode 721: Accounts Merge

Problem Restatement We are given a list of accounts. Each account has this format: [name, email1, email2, ...] Two accounts belong to the same person if they share at least one email address. After merging accounts, each returned account should contain: The person's name. All unique emails belonging to that person, sorted lexicographically. The returned accounts can be in any order. Accounts with the same name do not automatically belong...

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LeetCode 990: Satisfiability of Equality Equations

Problem Restatement We are given an array of equations. Each equation has exactly four characters and is one of two forms: "a==b" "a!=b" Each variable is a lowercase English letter. We need to return True if it is possible to assign integer values to the variables so that all equations are satisfied. Otherwise, return False . For example: ["a==b", "b!=a"] cannot be satisfied, because the first equation says a and...

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LeetCode 815: Bus Routes

Problem Restatement We are given a list of bus routes. Each routes[i] is the route of bus i . The bus repeats this route forever. For example: routes[0] = [1, 5, 7] means bus 0 travels like this forever: 1 -> 5 -> 7 -> 1 -> 5 -> 7 -> ... We start at bus stop source . We are not on any bus initially. We want to reach...

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LeetCode 743: Network Delay Time

Problem Restatement We are given a directed weighted graph with n nodes labeled from 1 to n . The input times contains directed edges: [u, v, w] This means a signal can travel from node u to node v in w time. A signal starts from node k . We need to return the minimum time needed for all nodes to receive the signal. If some node cannot receive the...

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LeetCode 742: Closest Leaf in a Binary Tree

Problem Restatement We are given the root of a binary tree and an integer k . The value k exists somewhere in the tree. We need to return the value of the leaf node closest to the node whose value is k . A leaf node is a node with no children. Distance means the number of edges between nodes. The closest leaf may be: inside the target node's subtree,...

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LeetCode 913: Cat and Mouse

Problem Restatement We are given an undirected graph. Mouse starts at node 1 . Cat starts at node 2 . The hole is node 0 . Mouse moves first. Then Cat moves. They alternate turns. On each turn, the current player must move along one graph edge. Cat is not allowed to move into node 0 . The game ends in one of three ways: Result Condition Mouse wins Mouse...

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LeetCode 863: All Nodes Distance K in Binary Tree

Problem Restatement We are given the root of a binary tree, a target node, and an integer k . We need to return the values of all nodes whose distance from the target node is exactly k . Distance means the number of edges on the path between two nodes. The answer can be returned in any order. Input and Output Item Meaning Input root , the root of the...

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LeetCode 787: Cheapest Flights Within K Stops

Problem Restatement We are given n cities labeled from 0 to n - 1 . We are also given a list of directed flights. Each flight is represented as: [from_city, to_city, price] We need to find the cheapest price to travel from src to dst using at most k stops. A stop means an intermediate city between src and dst . So at most k stops means at most k...

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LeetCode 936: Stamping The Sequence

Problem Restatement We are given two strings: stamp target Initially, we start with a string made entirely of question marks: "?????" with the same length as target . In one move, we may place the stamp string over any position and overwrite the characters. For example: stamp = "abc" before = "?????" after = "??abc" The goal is to build target . We must return a sequence of stamping positions...

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LeetCode 959: Regions Cut By Slashes

Problem Restatement We are given an n x n grid. Each cell contains one of three characters: "/" "\\" " " A slash divides a square cell into smaller regions. A blank cell has no internal wall. We need to return how many connected regions exist in the whole grid. The official constraints are: Constraint Value n == grid.length == grid[i].length The grid is square 1 <= n <= 30...

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LeetCode 886: Possible Bipartition

Problem Restatement We are given n people labeled from 1 to n . We are also given a list dislikes , where each pair: [a, b] means person a dislikes person b , and person b dislikes person a . We need to split everyone into two groups so that no pair of people who dislike each other are in the same group. Return true if this is possible. Otherwise,...

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LeetCode 737: Sentence Similarity II

Problem Restatement We are given two sentences represented as arrays of words: sentence1 sentence2 We are also given a list of similar word pairs: similarPairs Each pair: [x, y] means word x is similar to word y . Two sentences are similar if: They have the same number of words. For every index i , sentence1[i] is similar to sentence2[i] . A word is always similar to itself. Similarity is...

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LeetCode 935: Knight Dialer

Problem Restatement We place a chess knight on a phone keypad. The keypad is arranged like this: 1 2 3 4 5 6 7 8 9 0 The knight moves in the same L-shape as in chess. We may start on any digit from 0 to 9 . Each time the knight lands on a digit, that digit is pressed. Given an integer n , return how many distinct phone...

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LeetCode 785: Is Graph Bipartite?

Problem Restatement We are given an undirected graph as an adjacency list. graph[i] contains all nodes connected to node i . We need to return True if the graph is bipartite. A graph is bipartite if its nodes can be split into two groups such that every edge connects nodes from different groups. Equivalently, we need to check whether we can color every node using two colors so that no...

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LeetCode 834: Sum of Distances in Tree

Problem Restatement We are given an undirected connected tree with n nodes labeled from 0 to n - 1 . The array edges has n - 1 edges, where each edge connects two nodes. We need to return an array answer of length n , where: answer[i] is the sum of distances from node i to every other node in the tree. Input and Output Item Meaning Input n and...

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LeetCode 934: Shortest Bridge

Problem Restatement We are given an n x n binary matrix grid . Each cell is either: 0 or: 1 A 1 represents land. A 0 represents water. An island is a group of 1 s connected in four directions: up down left right The grid contains exactly two islands. We may flip water cells from 0 to 1 . Return the smallest number of water cells we must flip...

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LeetCode 909: Snakes and Ladders

Problem Restatement We are given an n x n board for a Snakes and Ladders game. The squares are numbered from 1 to n^2 in a boustrophedon order. That means the numbering starts from the bottom-left square, goes left to right on one row, then right to left on the next row, alternating direction each row. From a square curr , one dice roll can move to any square from:...

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LeetCode 685: Redundant Connection II

Problem Restatement We are given a directed graph that started as a rooted tree with n nodes. A rooted tree has these properties: Property Meaning One root Exactly one node has no parent One parent per non-root node Every other node has exactly one parent Reachability Every node is reachable from the root No cycle Following directed edges never loops Then one extra directed edge was added. We need to...

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LeetCode 882: Reachable Nodes In Subdivided Graph

Problem Restatement We are given an undirected graph with original nodes numbered from 0 to n - 1 . Each edge is written as: [u, v, cnt] This means the original edge between u and v is subdivided by adding cnt new nodes between them. For example: [0, 1, 3] becomes: 0 - x1 - x2 - x3 - 1 So moving from 0 to 1 through this edge takes...

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LeetCode 684: Redundant Connection

Problem Restatement We are given an undirected graph. The graph originally started as a tree with n nodes: Property Meaning Connected Every node can be reached No cycles Exactly one path between any two nodes Then one extra edge was added. The input edges contains all edges of the resulting graph. We must return the edge that can be removed so the graph becomes a tree again. If multiple answers...

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LeetCode 854: K-Similar Strings

Problem Restatement We are given two strings s1 and s2 . The two strings are anagrams. That means they contain the same letters with the same frequencies. One operation lets us swap any two characters in s1 . We need to return the smallest number of swaps needed to turn s1 into s2 . This smallest number is called k . For example: s1 = "abc" s2 = "bca" One...

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LeetCode 928: Minimize Malware Spread II

Problem Restatement We are given an undirected graph with n nodes. The graph is represented as an adjacency matrix: graph[i][j] == 1 means node i is directly connected to node j . Some nodes are initially infected by malware. These nodes are listed in: initial Malware spreads through edges. If an infected node is connected to an uninfected node, the uninfected node also becomes infected. This continues until no more...

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LeetCode 778: Swim in Rising Water

Problem Restatement We are given an n x n grid. Each cell grid[i][j] is the elevation of that square. Rain starts falling. At time t , the water level is also t . We can swim from one cell to a 4-directionally adjacent cell only if both cells have elevation at most t . We start at the top-left cell: (0, 0) We want to reach the bottom-right cell: (n...

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LeetCode 547: Number of Provinces

Problem Restatement We are given an n x n matrix called isConnected . There are n cities. If: isConnected[i][j] == 1 then city i and city j are directly connected. A province is a group of cities that are directly or indirectly connected to each other, with no city outside the group connected to them. We need to return the number of provinces. This is the same as counting connected...

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LeetCode 568: Maximum Vacation Days

Problem Restatement We are given two matrices: Matrix Meaning flights Whether we can fly from one city to another days How many vacation days we can take in each city during each week There are n cities, indexed from 0 to n - 1 . We start in city 0 on Monday morning before week 0 . Each week, we may either: Stay in the current city. Fly to another...

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LeetCode 753: Cracking the Safe

Problem Restatement We have a safe protected by an unknown password. The password has length n . Each digit can be one of: 0, 1, ..., k - 1 When we type digits into the safe, it checks the most recent n digits after every key press. For example, if the password is: 345 and we type: 012345 then the safe checks: 012 123 234 345 When it sees 345...

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LeetCode 505: The Maze II

Problem Restatement We are given a maze represented as a grid. Value Meaning 0 Empty space 1 Wall A ball starts at position start . The goal is to reach position destination . The ball does not move one cell at a time. Instead, once the ball starts moving in a direction, it keeps rolling until it hits a wall. Only then can it choose another direction. We need to...

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LeetCode 802: Find Eventual Safe States

Problem Restatement We are given a directed graph with n nodes labeled from 0 to n - 1 . The graph is represented as an adjacency list: graph[i] contains every node that node i points to. A terminal node has no outgoing edges. A safe node is a node where every possible path starting from that node eventually reaches a terminal node. If a node can reach a cycle, then...

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LeetCode 752: Open the Lock

Problem Restatement We have a lock with four wheels. Each wheel contains digits from 0 to 9 . The lock starts at: "0000" In one move, we can rotate exactly one wheel by one step. The digits wrap around: 9 -> 0 0 -> 9 Some lock states are deadends. If the lock reaches one of those states, it gets stuck and cannot move anymore. Given a list of deadends...

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LeetCode 851: Loud and Rich

Problem Restatement We are given n people labeled from 0 to n - 1 . Each person has: Data Meaning quiet[i] Quietness level of person i richer[j] = [a, b] Person a is richer than person b For every person x , we need to find the quietest person among all people who are at least as rich as x . This includes: Person x Everyone directly richer than x...

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LeetCode 582: Kill Process

Problem Restatement We are given a list of process IDs and their parent process IDs. Each process forms part of a process tree. If a process is killed, then all of its child processes are also killed recursively. Given a process ID called kill , return all process IDs that will be terminated. The result may be returned in any order. The official problem defines: pid[i] = process ID ppid[i]...

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LeetCode 399: Evaluate Division

Problem Restatement We are given equations representing division relationships between variables. For example: a / b = 2.0 b / c = 3.0 We are also given queries like: a / c c / a a / e We need to compute the value of each query. If the query cannot be determined from the equations, return: -1.0 The equations are guaranteed to be valid, and there is no contradiction....

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LeetCode 499: The Maze III

Problem Restatement We are given a maze represented by a 2D grid. Value Meaning 0 Empty cell 1 Wall A ball starts at ball . There is also a hole at hole . The ball can roll in four directions: Letter Direction u Up d Down l Left r Right Once the ball starts rolling, it keeps moving in that direction until one of two things happens: It hits a...

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LeetCode 323: Number of Connected Components in an Undirected Graph

Problem Restatement We are given: n edges There are n nodes labeled: 0 to n - 1 edges describes an undirected graph. Return the number of connected components. A connected component is a maximal group of nodes where every node can reach every other node in the group. The official problem defines the graph as undirected with nodes labeled from 0 to n - 1 . Input and Output Item...

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LeetCode 417: Pacific Atlantic Water Flow

Problem Restatement We are given an m x n matrix heights . Each cell represents land height. Water can flow from one cell to another adjacent cell if the next cell has height less than or equal to the current cell. Adjacent means four directions only: up, down, left, right The Pacific Ocean touches the top and left edges. The Atlantic Ocean touches the bottom and right edges. Return all...

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LeetCode 444: Sequence Reconstruction

Problem Restatement We are given: Name Meaning nums The target sequence sequences A list of subsequences The array nums is a permutation of integers from 1 to n . Each sequence in sequences is a subsequence of nums . We need to check whether nums is the only shortest supersequence that contains every sequence in sequences as a subsequence. A supersequence means it contains another sequence in the same relative...

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LeetCode 317: Shortest Distance from All Buildings

Problem Restatement We are given an m x n grid. Each cell has one of three values: Value Meaning 0 Empty land 1 Building 2 Obstacle We want to build a house on an empty land cell. The house must be able to reach every building by moving only up, down, left, and right. Buildings and obstacles cannot be passed through. Return the minimum total travel distance from one empty...

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LeetCode 490: The Maze

Problem Restatement We are given a maze represented by a 2D grid. Each cell has one of two values: Value Meaning 0 Empty space 1 Wall A ball starts at start . The ball can roll in four directions: Direction Up Down Left Right But the ball does not move one cell and stop. Once it starts rolling in a direction, it keeps rolling until it hits a wall. It...

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LeetCode 269: Alien Dictionary

Problem Restatement We are given a list of words sorted according to an unknown alien alphabet. We need to infer one possible order of the alien alphabet. Return a string containing all unique letters in a valid order. If no valid order exists, return: "" If multiple valid orders exist, any one of them is accepted. The constraints are 1 <= words.length <= 100 , 1 <= words[i].length <= 100...

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LeetCode 286: Walls and Gates

Problem Restatement We are given an m x n grid called rooms . Each cell has one of three values: Value Meaning -1 Wall or obstacle 0 Gate 2147483647 Empty room, also called INF We need to fill each empty room with the distance to its nearest gate. Distance is the number of steps needed to reach a gate by moving only up, down, left, or right. If an empty...

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LeetCode 200: Number of Islands

Problem Restatement We are given an m x n grid. Each cell is one of two characters: Character Meaning "1" Land "0" Water We need to count how many islands exist in the grid. An island is a group of land cells connected horizontally or vertically. Diagonal connection does not count. The official problem asks for the number of islands in a binary grid of land and water. Input and...

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LeetCode 210: Course Schedule II

Problem Restatement We are given: numCourses prerequisites Each prerequisite pair: [a, b] means: to take course a, you must first complete course b We must return a valid order in which all courses can be completed. If it is impossible because of a cycle, return an empty list. The official statement says: return any valid ordering of courses that allows completion of all courses. If no ordering exists, return an...

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LeetCode 261: Graph Valid Tree

Problem Restatement We are given: An integer n A list of undirected edges The graph has nodes labeled from 0 to n - 1 . Each edge: [a, b] means there is an undirected connection between node a and node b . We need to return True if these edges form a valid tree. Otherwise, return False . A valid tree must satisfy two properties: Property Meaning Connected Every node...

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LeetCode 310: Minimum Height Trees

Problem Restatement We are given a tree with n nodes labeled from 0 to n - 1 . The tree is given as an undirected edge list edges , where: edges[i] = [a, b] means node a and node b are connected. We may choose any node as the root. The height of the rooted tree is the number of edges on the longest downward path from the root to...

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LeetCode 133: Clone Graph

Problem Restatement We are given a reference to a node in a connected undirected graph. Each node has: Field Meaning val Integer value of the node neighbors List of neighboring node references We need to return a deep copy of the graph. A deep copy means: Every original node gets a new node object. Every edge is copied between the new node objects. No cloned node should point back to...

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LeetCode 207: Course Schedule

Problem Restatement We are given: numCourses a list of prerequisite pairs Each pair: [a, b] means: to take course a, you must first complete course b We need to determine whether it is possible to finish all courses. The official statement says: there are numCourses courses labeled from 0 to numCourses - 1 . You are given an array prerequisites where prerequisites[i] = [ai, bi] indicates that you must take...

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LeetCode 407: Trapping Rain Water II

Problem Restatement We are given an m x n matrix called heightMap . Each cell represents the height of one unit block in a 2D elevation map. After rain, water may be trapped in lower cells if surrounding boundaries prevent it from flowing out. Return the total amount of trapped water. Water can move through the four main directions: up, down, left, right Diagonal movement does not matter. Boundary cells...

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LeetCode 332: Reconstruct Itinerary

Problem Restatement We are given a list of airline tickets. Each ticket is a pair: [from, to] meaning there is a flight from airport from to airport to . We need to reconstruct the itinerary in order. Rules: Rule Meaning Start airport The itinerary must start from "JFK" Use all tickets Every ticket must be used exactly once Lexicographic order If multiple valid itineraries exist, return the smallest one Guarantee...

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LeetCode 305: Number of Islands II

Problem Restatement We are given an empty m x n grid filled with water. Each operation turns one cell into land. After every operation, return the current number of islands. An island is a group of connected land cells connected horizontally or vertically. The official problem defines: Value Meaning 0 Water 1 Land The grid starts entirely with water. For each position in positions , we add land at that...

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LeetCode 127: Word Ladder

Problem Restatement We are given: Name Meaning beginWord Starting word endWord Target word wordList Dictionary of allowed words We may transform one word into another by changing exactly one character. Every transformed word must exist in wordList . We need to return the number of words in the shortest transformation sequence from beginWord to endWord . If no valid sequence exists, return 0 . Examples Example 1: beginWord = "hit"...

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LeetCode 277: Find the Celebrity

Problem Restatement There are n people at a party, labeled from 0 to n - 1 . A celebrity is a person who satisfies two conditions: Everyone else knows the celebrity. The celebrity knows nobody else. We are given an API: knows(a, b) It returns True if person a knows person b . We need to implement: findCelebrity(n) Return the celebrity label if one exists. Otherwise, return -1 . The...

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LeetCode 126: Word Ladder II

Problem Restatement We are given three things: Name Meaning beginWord The word where the transformation starts endWord The word we want to reach wordList The dictionary of valid transformed words We need to return all shortest transformation sequences from beginWord to endWord . A valid transformation sequence looks like this: beginWord -> s1 -> s2 -> ... -> endWord Each step must obey two rules: Adjacent words must differ by...

#graph

LeetCode 1059: All Paths from Source Lead to Destination

LeetCode 1042: Flower Planting With No Adjacent

LeetCode 847: Shortest Path Visiting All Nodes

LeetCode 924: Minimize Malware Spread

LeetCode 997: Find the Town Judge

LeetCode 841: Keys and Rooms

LeetCode 947: Most Stones Removed with Same Row or Column

LeetCode 996: Number of Squareful Arrays

LeetCode 839: Similar String Groups

LeetCode 994: Rotting Oranges

LeetCode 773: Sliding Puzzle

LeetCode 797: All Paths From Source to Target

LeetCode 943: Find the Shortest Superstring

LeetCode 721: Accounts Merge

LeetCode 990: Satisfiability of Equality Equations

LeetCode 815: Bus Routes

LeetCode 743: Network Delay Time

LeetCode 742: Closest Leaf in a Binary Tree

LeetCode 913: Cat and Mouse

LeetCode 863: All Nodes Distance K in Binary Tree

LeetCode 787: Cheapest Flights Within K Stops

LeetCode 936: Stamping The Sequence

LeetCode 959: Regions Cut By Slashes

LeetCode 886: Possible Bipartition

LeetCode 737: Sentence Similarity II

LeetCode 935: Knight Dialer

LeetCode 785: Is Graph Bipartite?

LeetCode 834: Sum of Distances in Tree

LeetCode 934: Shortest Bridge

LeetCode 909: Snakes and Ladders

LeetCode 685: Redundant Connection II

LeetCode 882: Reachable Nodes In Subdivided Graph

LeetCode 684: Redundant Connection

LeetCode 854: K-Similar Strings

LeetCode 928: Minimize Malware Spread II

LeetCode 778: Swim in Rising Water

LeetCode 547: Number of Provinces

LeetCode 568: Maximum Vacation Days

LeetCode 753: Cracking the Safe

LeetCode 505: The Maze II

LeetCode 802: Find Eventual Safe States

LeetCode 752: Open the Lock

LeetCode 851: Loud and Rich

LeetCode 582: Kill Process

LeetCode 399: Evaluate Division

LeetCode 499: The Maze III

LeetCode 323: Number of Connected Components in an Undirected Graph

LeetCode 417: Pacific Atlantic Water Flow

LeetCode 444: Sequence Reconstruction

LeetCode 317: Shortest Distance from All Buildings

LeetCode 490: The Maze

LeetCode 269: Alien Dictionary

LeetCode 286: Walls and Gates

LeetCode 200: Number of Islands

LeetCode 210: Course Schedule II

LeetCode 261: Graph Valid Tree

LeetCode 310: Minimum Height Trees

LeetCode 133: Clone Graph

LeetCode 207: Course Schedule

LeetCode 407: Trapping Rain Water II

LeetCode 332: Reconstruct Itinerary

LeetCode 305: Number of Islands II

LeetCode 127: Word Ladder

LeetCode 277: Find the Celebrity

LeetCode 126: Word Ladder II