Depth-First Search
Explore as far as possible down one path before backtracking, used to walk trees, graphs, and grids.
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Union-Find (Disjoint Set)
Track which nodes belong to the same group and merge groups quickly, used to detect cycles and build networks.
Union-Find (Disjoint Set) Practice Problems
Easy
1 problemsMedium
7 problems- 98medium
Number of Provinces
Count how many groups of directly or indirectly connected cities exist.
- 99medium
Redundant Connection
Find the extra edge that turns a tree of connections into one with a cycle.
- 100medium
Accounts Merge
Merge accounts that share at least one email address into a single account.
- 101medium
Graph Valid Tree
Check whether a given set of edges and nodes forms a valid tree.
- 255medium
Number of Connected Components in an Undirected Graph
Count the number of connected components in an undirected graph.
- 256medium
Satisfiability of Equality Equations
Determine whether a list of equality and inequality equations can all be satisfied.
- 257medium
Smallest String With Swaps
Find the lexicographically smallest string reachable by swapping indices given as pairs.
Hard
1 problemsRelated concepts
Breadth-First Search
Explore level by level from a starting point, the go-to way to find the shortest path in an unweighted graph.
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Dijkstra's Algorithm
Find the shortest path from a starting node to every other node in a graph where edges have non-negative weights.
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Bellman-Ford Algorithm
Find the shortest path from a starting node even when some edges have negative weights, and detect negative cycles.
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Topological Sort
Order the nodes of a graph so every task comes after everything it depends on, used for scheduling and build order.
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Kruskal's Algorithm
Build the cheapest network connecting all nodes by adding the smallest edges first, skipping any that form a cycle.
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