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This approach leverages Tarjan's Algorithm to find bridges in an undirected graph. A bridge, also known as a critical connection, is an edge which, when removed, increases the number of connected components in a graph.
The main idea is to use a DFS traversal while keeping track of two things for each node:
During the DFS traversal, if a node discovers a node that was discovered earlier, we update the current node's lowest point based on the discovered node unless it is a direct parent of the current node which means it's a backtracking edge. If the lowest point of the descendant is greater than the discovery time of the current node, then the connection between them is a critical connection.
The time complexity is O(V + E) where V is the number of vertices and E is the number of edges. The space complexity is also O(V + E) due to the graph representation and recursion stack.
1import java.util.*;
2
3class Solution {
4 public List<List<Integer>> criticalConnections(int n, List
The Java implementation leverages maps and lists to construct the graph and uses similar logic for DFS traversal as previous implementations.
The Union-Find approach is less direct for this problem as it better suits static connectivity queries, but it can verify the disconnection effect of removing an edge by checking connectivity before and after its removal.
Here, a variation of Kruskal's algorithm can be employed with additional tracking to retry connections and verify their critical status. However, this requires additional complexity and is not the standard usage for critical connections.
So, while possible, using Union-Find isn't recommended due to its inefficiency in recomputing components with high time complexity.
The time complexity on worst-case is O(E^2) due to the need for reconstructing the Union-Find structure. The space complexity is O(V) for the Union-Find structure.
1class UnionFind:
2
The code implements a brute-force check of each edge's removal effect by rebuilding a Union-Find structure for each remaining connection set. It provides an intuitive understanding though not efficient for large inputs.