Singapore MRT

This application aims to determine the best route between two stations in Singapore's MRT.

Getting Started

The project is based on Typescript and uses Node.js v10 in order to execute.

Prerequisites

Node v10.x & NPM v6.x

How to install Node & NPM on Ubuntu 16.04?

The following commands will install both Node v10.x and NPM are on Ubuntu 16.04.

curl -sL https://deb.nodesource.com/setup_10.x | sudo -E bash -

sudo apt-get install -y nodejs

You can verify the installation using the following commands:

node --version 
# Prints Node version like (v10.15.3)

npm --version 
# Prints NPM version like (6.4.1)

Installing

Install dependencies:

# From the project root directory
npm install

Running the tests

Automated tests for the project can be run using:

# From the project root directory
npm test

Running the solution

Running the solution involves two steps:

Build (Transpile TypeScript into JavaScript)
Running the build output (javascript)

Build

You can build the project using the following command:

# From the project root directory
npm run build

Run

You can run the transpiled code using the following command:

# From the project root directory
npm start

Usage

The easiest way to use the solution is npm start. Source station, Destination station and start-time (optional) are the arguments accepted by the solution. You can provide the start-time in YYYY-MM-DDThh:mm format. In case no arguments are provided, you will be prompted for the same.

# Be prompted for arguments
npm start

# Provide arguments while starting the solution 
# Without providing start-time
npm start -- route "Holland Village" "Bugis"

# With start-time
npm start -- route "Holland Village" "Bugis" --start-time "2019-01-01T08:00"

Assumptions

The following assumptions were made during the development:

Time taken per stop, time taken per line change and the opening dates only come into effect when the start time is provided.
If the start time is not provided, the time taken per stop and the time taken to change lines, both are assumed to be 1 minute. The opening date for the stop is ignored.
Trains cannot travel through stations which are not open. Example: If the following is a train line: Station A -> Station B -> Station C. If Station B is not open yet, there is no route between Station A and Station C.

Terminology

The following terminology is used in the code:

Line: The route that metro trains will take. (Eg: Circle Line, NorthSouth Line, etc.)
Line Code: The first two letters of all the stops in the line. (Eg: The line NS1 -> NS2 -> ... has NS as the line code)
Line Stop/Stop: All the stops made by a particular line. This is the place where users embark and disembark. (Eg: The line NS1 -> NS2 -> ... has [NS1, NS2, ...] as the line stops)
Station: A station is home to one or more Line Stops. Any stations which has more than 1 stop, is an intersection station.
Intersection Line: Intersection Line is a virtual line used to connect two stops of the same station. This concept is used to make line-change possible in the searching algorithm used. (Eg: Little India is home to two stops: NE7 & DT12. While searching for an optimal route, an intersection line is used to connect NE7 & DT12).

Known Issues

Here are the known issues with the solution:

Line Closing Time

In case a train line is closing or opening in some time (due to night hours), but the start-time provided is just before the closing time, the solution only takes into account the train lines which were open at the start-time provided. Any lines closure/opening that happens after the start-time is not taken into account while determining the route.

Example:

Suppose a user is trying to go from Caldecott to Newton at 2019-01-01T21:59. The optimum route, without considering the line closure which takes place at 22:00, would be CC17 -> CC19 -> DT9 -> DT10 -> DT11. However, since the DT line closes at 22:00, the user will not be able to switch to the DT line.

ashraymehta/singapore-mrt