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Understand the problem
Restate the problem precisely. Interviewers reward candidates who pause, define the contract, and name the guarantees before coding.
You are given a network of `n` nodes, labeled from `1` to `n`. You are also given `times`, a list of travel times as directed edges `times[i] = [uᵢ, vᵢ, wᵢ]`, where `uᵢ` is the source node, `vᵢ` is the target node, and `wᵢ` is the time it takes for a signal to travel from source to target. We will send a signal from a given node `k`. Return the time it takes for all the `n` nodes to receive the signal. If it is impossible for all the `n` nodes to receive the signal, return `-1`.
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