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pb071(pexam): add prep exam for seminar
Signed-off-by: Matej Focko <xfocko@fi.muni.cz>
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pb071/pexam/_category_.yaml
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pb071/pexam/_category_.yaml
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label: Practice Exams
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position: 1
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link:
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type: generated-index
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description: |
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Practice exams for training for the final exam.
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pb071/pexam/c-watching_cams.md
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pb071/pexam/c-watching_cams.md
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---
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title: Practice exam C
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description: |
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Stalking cars…
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---
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# Watching Cams
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:::caution Exam environment
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* During the exam you will be provided with a barebone _exam session_ on the
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_faculty computers_.
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* In browser you are only allowed to have the following tabs open:
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* [C documentation](https://en.cppreference.com)
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* page containing the assignment
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* You **are not** allowed to use your own source code, e.g. prepared beforehand
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or from the seminars.
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* You have **5 minutes** to read through the assignment and ask any follow-up
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questions should be there something unclear.
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* You have **60 minutes** to work on the assignment, afterward your work will be
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discussed with your seminar tutor.
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:::
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Your task is to write a program `cams` that will be processing input from the
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cams that are capable of identifying license plates on the cars and then
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evaluate the queries on the given data. Your contributions to the society are
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very much appreciated and may (or may not) be used for (each or none) of the
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following purposes:
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* stalking people leaving and coming back home,
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* retroactively making people pay for the parking,
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* providing evidence of people speeding on highways,
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* tracking people that don't pay tolls, or
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* convict employees leaving the work prematurely.
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## Format of the input files
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Input for your program consists of the data from the cameras and queries. You
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will be **always** given the data from the cameras as a path to a file, whereas
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user should be able to specify `-` (i.e. `stdin`) as the path to queries.
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:::tip Validation of data
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For the sake of simplicity (and partially relieving the time pressure), you
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**are not** required to validate the dates you are given on the input (e.g. leap
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years, days in months, etc.).
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This is caused by the fact that you will be given just a timestamp that you
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**don't** need to process in any (other than suggested ways for debugging).
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:::
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### Data from the cameras
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Each “scan” (i.e. reading) of the cameras consists of the following data:
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* _camera ID_: non-negative integer identifying a camera
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* _plate_: string of unknown length that can consist of any characters apart
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from whitespace
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* _timestamp_: timedate of the scan as an unsigned integer (represented as a
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UNIX time)
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:::tip
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When programming on UN\*X(-like) systems, you can assume that the `time_t`
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structure from the system header `time.h` **is** the `unsigned int` that you
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are provided in the input file.
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:::
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And they are compiled into one reading such as:
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camera_ID: plate timestamp
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There should be always **at least one** space in between each part of the
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reading. Reading are separated by the commas, which may, but don't have to, be
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accompanied by whitespace around.
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#### Examples
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Few examples of the data from the cameras follow
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```
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10: ABC-12-34 1664608712, 289: XYZ-98-76 1665416417,
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25: ABC-12-34 1633078256 , 42: TryToCatchMe 1671602419,
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11: EL9-987 1679541338 ,2 : Foo-666 1683170082,42: YourMum 1683170082,
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42: TryToCatchMe 1671602419 , 1234: TryToCatchMe 1671602419,
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19: ABC-12-34 1664659649, 69:YouShould-not-pLaCe-4ny-expectations%on^the(input 1680307994,
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9 : 9B9-161 1665416417 , 10: 1a1-999 1671602419,1:lmao 1633078256
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```
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### Queries
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Querying the processed data is done by providing a license plate. You can expect
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that the license plates are separated by `\n` (newline, also known as
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_ňjůlajn_) **with no other whitespace around**.
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#### Examples
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Few examples of the queries follow
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ABC-12-34
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TryToCatchMe
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Foo-666
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EL9-987
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## Format of the output
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:::info
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All the examples above consider using data from the first example of the input.
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:::
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You may encounter these situations (and handle them in the following order):
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1. License plate was not found
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```
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404-not-found
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*** 404-not-found ***
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License plate was not found.
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```
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1. License plate was found
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In such case, you are expected to print out the dates and cameras that has
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captured the license plate.
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If there are multiple scans present and the timespan (i.e. time difference
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between the scans is bigger than 60 minutes, you are to separate them by a
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newline).
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```
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ABC-12-34
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*** ABC-12-34 ***
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25: Fri Oct 1 10:50:56 2021
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10: Sat Oct 1 09:18:32 2022
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19: Sat Oct 1 23:27:29 2022
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```
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:::tip
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Since you are given the timestamp in a `time_t` compatible type on UN\*X, you
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can safely use `ctime` for printing the timestamp as a _human readable_ time
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when outputting the date and time.
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:::
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:::tip
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For a better readability you can include one more newline after the last line
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of the output.
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:::
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## Example usage
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You can also have a look at example usage of your program. We can run your
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program from the shell like
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$ ./cams example_1.txt -
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And then provide the queries, since we specified `-` as the file for the queries
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> ABC-12-34
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*** ABC-12-34 ***
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25: Fri Oct 1 10:50:56 2021
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10: Sat Oct 1 09:18:32 2022
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19: Sat Oct 1 23:27:29 2022
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> NonExistentLicensePlate
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*** NonExistentLicensePlate ***
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License plate was not found.
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> EL9-987
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*** EL9-987 ***
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11: Thu Mar 23 04:15:38 2023
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> TryToCatchMe
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*** TryToCatchMe ***
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42: Wed Dec 21 07:00:19 2022
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42: Wed Dec 21 07:00:19 2022
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1234: Wed Dec 21 07:00:19 2022
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:::info
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Lines prefixed with `> ` in the example above represent the user input.
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:::
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## Requirements and notes
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* Define **structures** (and **enumerations**, if applicable) for the parsed
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information from the files.
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* For keeping the “records”, use some **dynamic** data structure.
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* Don't forget to consider pros and cons of using _specific_ data structures
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before going through implementing.
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* You **are not required** to produce 1:1 output to the provided examples, they
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are just a hint to not waste your time tinkering with a user experience.
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* If any of the operations on the input files should fail,
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**you are expected to** handle the situation _accordingly_.
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* Failures of any other common functions (e.g. functions used for memory
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management) should be handled in **the same way** as they were in the
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homeworks and seminars.
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* Your program **must free** all the resources before exiting.
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