Sensor Network I
Field sensors numbered 0 to n − 1 are linked by undirected edges (u, v). Return whether the network contains a cycle.
n = 5, edges = [[0, 1], [1, 2], [2, 0]] -> true (a triangle) n = 4, edges = [[0, 1], [2, 3]] -> false
A self-loop, or the same link listed twice, counts as a cycle.
Hints
Hint 1
Union-Find: process the edges one at a time. If both endpoints already have the same root, this edge closes a cycle.
Hint 2
DFS works too, as long as you ignore the edge you arrived by — but a duplicate link then needs care, which Union-Find handles for free.