问题描述
我想计算给定模型铁路上的可用路线。
I want to calculate the available routes on a given model railway.
假设:
- 所有火车仅在称为火车站的已定义点上开始和停止。
- 火车在旅行过程中不会发生碰撞。不必担心。
- 我们不必考虑火车的长度。我们假设它是一个占据原子空间的机车。
- 在一个火车站上,只有一列火车可以停下来。
- 火车可以启动在同一火车站停下。
- All trains only start and stop on defined points which are called train stations.
- Trains do not collide during their trip. No need to worry about that.
- We don't have to think about the length of a train. We assume it is one locomotive which takes the space of an atom.
- On one train station only one train can stop.
- A train can start and stop on the same train station.
所有火车的开始位置和结束位置都存储在地图中。所有排列都存储在列表中。示例:
The start position and the end position of all trains are stored in a map. All permutations are stored in a list. Example:
iex(1)> Trains.list_routes(["ICE"], ["Hamburg", "Frankfurt"])
[
%{end: %{"ICE" => "Hamburg"}, start: %{"ICE" => "Hamburg"}},
%{end: %{"ICE" => "Frankfurt"}, start: %{"ICE" => "Frankfurt"}},
%{end: %{"ICE" => "Frankfurt"}, start: %{"ICE" => "Hamburg"}},
%{end: %{"ICE" => "Hamburg"}, start: %{"ICE" => "Frankfurt"}}
]
铁路模型可能看起来像这样(红色数字表示火车站):
A model railway could look like this (the red numbers indicate the train stations):
对于该模型铁路上的两列火车,其功能为这样称呼:
For two trains on that model railway the function would be called this way:
Trains.list_routes([:red_train, :blue_train], ["1", "2", "3", "4", "5"])
这是我当前的代码:
defmodule Trains do
@moduledoc """
Documentation for `Trains`.
"""
@doc """
Returns a list of all possible routes.
## Examples
iex> Trains.list_routes([:red_train, :blue_train], ["Station 1", "Station 2"])
[
%{
end: %{blue_train: "Station 2", red_train: "Station 1"},
start: %{blue_train: "Station 2", red_train: "Station 1"}
},
%{
end: %{blue_train: "Station 1", red_train: "Station 2"},
start: %{blue_train: "Station 1", red_train: "Station 2"}
},
%{
end: %{blue_train: "Station 1", red_train: "Station 2"},
start: %{blue_train: "Station 2", red_train: "Station 1"}
},
%{
end: %{blue_train: "Station 2", red_train: "Station 1"},
start: %{blue_train: "Station 1", red_train: "Station 2"}
}
]
"""
def list_routes([], []) do
[]
end
def list_routes([train], [station]) do
[
%{start: %{train => station}, end: %{train => station}}
]
end
def list_routes([train], [station1, station2]) do
[
%{start: %{train => station1}, end: %{train => station1}},
%{start: %{train => station2}, end: %{train => station2}},
%{start: %{train => station1}, end: %{train => station2}},
%{start: %{train => station2}, end: %{train => station1}}
]
end
def list_routes([train1, train2], [station1, station2]) do
[
%{
start: %{train1 => station1, train2 => station2},
end: %{train1 => station1, train2 => station2}
},
%{
start: %{train1 => station2, train2 => station1},
end: %{train1 => station2, train2 => station1}
},
%{
start: %{train1 => station1, train2 => station2},
end: %{train1 => station2, train2 => station1}
},
%{
start: %{train1 => station2, train2 => station1},
end: %{train1 => station1, train2 => station2}
}
]
end
def list_routes(trains, train_stations) do
# ???
end
end
如何使用 list_routes遍历所有组合(火车,火车站)
,当火车
的数量和 train_stations
的数量更大时大于1?
How can I loop through all combinations with list_routes(trains, train_stations)
when the number of trains
and the number of train_stations
is bigger than 1?
推荐答案
以下是该问题的解决方案。它使用。
Here's a solution for the problem. It uses Formulae.
混合。 exs
def deps do
[{:formulae, "~> 0.8"}]
end
lib / trains.ex
def list_routes([], []) do
[]
end
def list_routes(trains, train_stations)
when is_list(trains) and
is_list(train_stations) and
length(train_stations) >= length(trains) do
possible_states =
Enum.map(Formulae.permutations(train_stations, length(trains)), &Enum.zip(trains, &1))
for state_start <- possible_states, state_end <- possible_states do
%{start: state_start, end: state_end}
end
end
结果:
iex(1)> Trains.list_routes([:red_train, :blue_train], ["Station 1", "Station 2"])
[
%{
end: [red_train: "Station 1", blue_train: "Station 2"],
start: [red_train: "Station 1", blue_train: "Station 2"]
},
%{
end: [red_train: "Station 2", blue_train: "Station 1"],
start: [red_train: "Station 1", blue_train: "Station 2"]
},
%{
end: [red_train: "Station 1", blue_train: "Station 2"],
start: [red_train: "Station 2", blue_train: "Station 1"]
},
%{
end: [red_train: "Station 2", blue_train: "Station 1"],
start: [red_train: "Station 2", blue_train: "Station 1"]
}
]
这篇关于列出给定模型铁路上可能的火车路线的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持!