Traffic signal shortest arrival
A courier travels a road network of n intersections (0..n-1) connected by bidirectional `roads` `[u, v, travel_time]`. Every intersection has a synchronized signal: during the first `red_period` time units of each `2*red_period` cycle it is green (you may depart), and during the second half it is red (you must wait at the intersection until the next green). The courier starts at intersection 0 at time 0 (green) and wants to reach intersection n-1. Return the earliest arrival time, or -1 if unreachable. Arriving at an intersection is always allowed; only departing is gated.
min_time_signals(n: int, roads: list[list[int]], red_period: int) → int[3,[[0,1,7],[1,2,4]],5]out14State your approach and its time/space complexity out loud before you optimize. Handle the edge cases (empty input, duplicates, overflow), and say why you chose this over the brute force. Green tests are the floor, not the grade.
[3,[[0,1,7],[1,2,4]],5]14not run yetsample