- Chief, we have a new flight schedule. It just require your signature and we are ready to launch.
- Wow, so many planes! I’d like to make sure that we really need so many of them.
- Of course.
- Let’s check!
This task is a continuation of the “Cheapest Flights” mission.
Here you have a flight schedule by which you need to find out whether all flights are really necessary.
For example: If from the point A to point C you can fly directly for $ 100, but you can also go through the point B (from A to B, and then from B to C) for $ 90, then connection A – C isn’t really needed. But if the price from A to C is $ 90 or less, then this connection remains on the schedule.
Input: An array of all possible connections. Each element in the array is also an array of 3 elements: the first city, second city and flight price.
Output: An array of the unnecessary flight indices.
useless_flight([['A', 'B', 50], ['B', 'C', 40], ['A', 'C', 100]]) ==  useless_flight([['A', 'B', 50], ['B', 'C', 40], ['A', 'C', 90]]) ==