npm ci
npm run testIn index.js, there are four incomplete methods: depend, install, list, and remove. Fill in an implementation for each method according to the Problem description below. You are allowed to change anything needed: create new variables, global variables, helper functions, as needed. The setUp and tearDown functions are called for each test case, so add anything in there if you need it.
Originally copied from Karrels 1997 ACM Finals, Problem A.
In this problem you'll implement a dependency management system. Software packages often have dependencies -- other packages that must be installed before they will function properly. These dependencies are frequently shared by multiple components. For example, the react package and the angular package require that the nodejs software be installed before they can operate. If you install react package, and later decide to add angular, you do not need to reinstall nodejs.
It is useful to be able to remove components that are no longer needed, to save disk space or memory space. But a supporting component, not explicitly installed, may be removed only if all components which depend on it are also removed. For example, removing the angular package and nodejs package would mean the react package, which was not removed, would no longer operate. Likewise, if we installed react to support our own development, then installed the angular client (which also depends on nodejs) and then still later removed the angular client, we would not want nodejs to be removed because it is still required.
You'll need to maintain a record of installed components and component dependencies. You'll also need to maintain a record of which packages depend on other packages.
The input will contain a sequence of commands (as described below), each called one by one. Item names are case sensitive, and each is no longer than ten characters. All appropriate DEPEND commands will appear before the occurrence of any INSTALL dependencies.
| Command Syntax | Interpretation/Response |
|---|---|
| DEPEND item1 item2 [item3 ...] | item1 depends on item2 (and item3 ...) |
| INSTALL item1 | install item1 and those on which it depends |
| REMOVE item1 | remove item1, and those on whch it depends, if possible |
| LIST | list the names of all currently-installed components |
Echo each line of input. Follow each echoed INSTALL or REMOVE line with the actions taken in response, making certain that the actions are given in the proper order. Also identify exceptional conditions (see Expected Output, below, for examples of all cases). For the LIST command, display the names of the currently installed components. No output, except the echo, is produced for a DEPEND command or the line containing END. There will be at most one dependency list per item.