From f4c253be5528c00789a66114a8f36b433e8334b0 Mon Sep 17 00:00:00 2001 From: glaxxie <86179463+glaxxie@users.noreply.github.com> Date: Mon, 13 Oct 2025 18:57:03 -0500 Subject: [PATCH] [New Exercise]: Intergalactic Transmission Add exercise `intergalactic transmission` --- config.json | 8 + .../.docs/instructions.md | 54 +++++ .../.docs/introduction.md | 23 ++ .../IntergalacticTransmission.example.ps1 | 87 ++++++++ .../.meta/config.json | 19 ++ .../.meta/tests.toml | 88 ++++++++ .../IntergalacticTransmission.ps1 | 43 ++++ .../IntergalacticTransmission.tests.ps1 | 197 ++++++++++++++++++ 8 files changed, 519 insertions(+) create mode 100644 exercises/practice/intergalactic-transmission/.docs/instructions.md create mode 100644 exercises/practice/intergalactic-transmission/.docs/introduction.md create mode 100644 exercises/practice/intergalactic-transmission/.meta/IntergalacticTransmission.example.ps1 create mode 100644 exercises/practice/intergalactic-transmission/.meta/config.json create mode 100644 exercises/practice/intergalactic-transmission/.meta/tests.toml create mode 100644 exercises/practice/intergalactic-transmission/IntergalacticTransmission.ps1 create mode 100644 exercises/practice/intergalactic-transmission/IntergalacticTransmission.tests.ps1 diff --git a/config.json b/config.json index a2a2575..9309188 100644 --- a/config.json +++ b/config.json @@ -1095,6 +1095,14 @@ "prerequisites": [], "difficulty": 5 }, + { + "slug": "intergalactic-transmission", + "name": "Intergalactic Transmission", + "uuid": "7ec4147a-392c-49f6-9587-f580ac61b48e", + "practices": [], + "prerequisites": [], + "difficulty": 5 + }, { "slug": "rectangles", "name": "Rectangles", diff --git a/exercises/practice/intergalactic-transmission/.docs/instructions.md b/exercises/practice/intergalactic-transmission/.docs/instructions.md new file mode 100644 index 0000000..5497088 --- /dev/null +++ b/exercises/practice/intergalactic-transmission/.docs/instructions.md @@ -0,0 +1,54 @@ +# Instructions + +Your job is to help implement + +- the transmitter, which calculates the transmission sequence, and +- the receiver, which decodes it. + +A parity bit is simple way of detecting transmission errors. +The transmitters and receivers can only transmit and receive _exactly_ eight bits at a time (including the parity bit). +The parity bit is set so that there is an _even_ number of 1 bits in each transmission, and the parity bit is always the first bit from the right. +So if the receiver receives `11000001`, `01110101` or `01000000` (i.e. a transmission with an odd number of 1 bits), it knows there is an error. + +However, messages are rarely this short, and need to be transmitted in a sequence when they are longer. + +For example, consider the message `11000000 00000001 11000000 11011110` (or `C0 01 C0 DE` in hex). + +Since each transmission contains exactly eight bits, it can only contain seven bits of data and the parity bit. +A parity bit must then be inserted after every seven bits of data: + +```text +11000000 00000001 11000000 11011110 + ↑ ↑ ↑ ↑ (7th bits) +``` + +The transmission sequence for this message looks like this: + +```text +1100000_ 0000000_ 0111000_ 0001101_ 1110 + ↑ ↑ ↑ ↑ (parity bits) +``` + +The data in the first transmission in the sequence (`1100000`) has two 1 bits (an even number), so the parity bit is 0. +The first transmission becomes `11000000` (or `C0` in hex). + +The data in the next transmission (`0000000`) has zero 1 bits (an even number again), so the parity bit is 0 again. +The second transmission thus becomes `00000000` (or `00` in hex). + +The data for the next two transmissions (`0111000` and `0001101`) have three 1 bits. +Their parity bits are set to 1 so that they have an even number of 1 bits in the transmission. +They are transmitted as `01110001` and `00011011` (or `71` and `1B` in hex). + +The last transmission (`1110`) has only four bits of data. +Since exactly eight bits are transmitted at a time and the parity bit is the rightmost bit, three 0 bits and then the parity bit are added to make up eight bits. +It now looks like this (where `_` is the parity bit): + +```text +1110 000_ + ↑↑↑ (added 0 bits) +``` + +There is an odd number of 1 bits again, so the parity bit is 1. +The last transmission in the sequence becomes `11100001` (or `E1` in hex). + +The entire transmission sequence for this message is `11000000 00000000 01110001 00011011 11100001` (or `C0 00 71 1B E1` in hex). diff --git a/exercises/practice/intergalactic-transmission/.docs/introduction.md b/exercises/practice/intergalactic-transmission/.docs/introduction.md new file mode 100644 index 0000000..f19dffb --- /dev/null +++ b/exercises/practice/intergalactic-transmission/.docs/introduction.md @@ -0,0 +1,23 @@ +# Introduction + +Trillions upon trillions of messages zip between Earth and neighboring galaxies every millisecond. +But transmitting over such long distances is tricky. +Pesky solar flares, temporal distortions, stray forces, and even the flap of a space butterfly's wing can cause a random bit to change during transmission. + +Now imagine the consequences: + +- Crashing the Intergalactic Share Market when "buy low" turns to "sell now". +- Losing contact with the Kepler Whirl system when "save new worm hole" becomes "cave new worm hole". +- Or plunging the universe into existential horror by replacing a cowboy emoji 🤠 with a clown emoji 🤡. + +Detecting corrupted messages isn't just important — it's critical. +The receiver _must_ know when something has gone wrong before disaster strikes. + +But how? +Scientists and engineers from across the universe have been battling this problem for eons. +Entire cosmic AI superclusters churn through the data. +And then, one day, a legend resurfaces — an ancient, powerful method, whispered in debugging forums, muttered by engineers who've seen too much... + +The Parity Bit! + +A method so simple, so powerful, that it might just save interstellar communication. diff --git a/exercises/practice/intergalactic-transmission/.meta/IntergalacticTransmission.example.ps1 b/exercises/practice/intergalactic-transmission/.meta/IntergalacticTransmission.example.ps1 new file mode 100644 index 0000000..7cdef36 --- /dev/null +++ b/exercises/practice/intergalactic-transmission/.meta/IntergalacticTransmission.example.ps1 @@ -0,0 +1,87 @@ +Function Invoke-Transmitter() { + <# + .SYNOPSIS + Implement the transmitter to calculates the transmission sequence. + + .DESCRIPTION + Implement a function that accept a sequence and encode it with parity bits to help detecting transmission errors. + + .PARAMETER Sequence + An array of hexadecimal values. + + .EXAMPLE + Invoke-Transmitter -Sequence @(0x05) + Returns: @(0x05, 0x81) + #> + [CmdletBinding()] + Param( + [byte[]]$Sequence + ) + [bigint]$buffer = 0 + [int]$bufferLen = 0 + $encoded = @() + foreach ($byte in $Sequence) { + $buffer = $buffer -shl 8 -bor $byte + $bufferLen += 8 + while ($bufferLen -ge 7) { + $shift = $bufferLen - 7 + $sevenBits = ($buffer -shr $shift) -band 0x7f + $parityBit = [System.Numerics.BitOperations]::PopCount([uint32]$sevenBits) -band 1 + $encodedByte = $sevenBits -shl 1 -bor $parityBit + $bufferLen -=7 + $encoded += $encodedByte + } + } + if ($bufferLen -gt 0) + { + $padRight = 7 - $bufferLen + $maskedBits = $buffer -band ((1 -shl $bufferLen) - 1) + $lastParityBit = [System.Numerics.BitOperations]::PopCount([uint32]$maskedBits) -band 1 + $encodedByte = $maskedBits -shl $padRight -shl 1 -bor $lastParityBit + $encoded += $encodedByte + } + $encoded +} + +Function Invoke-Receiver() { + <# + .SYNOPSIS + Implement the receiver to decode the transmission sequence. + + .DESCRIPTION + Implement a function to receive a sequence and decode it to the original message. + + .PARAMETER Sequence + An array of hexadecimal values. + + .EXAMPLE + Invoke-Receiver -Sequence @(0x05, 0x81) + Returns: @(0x05) + #> + [CmdletBinding()] + Param( + [byte[]]$Sequence + ) + [bigint]$buffer = 0 + [int]$bufferLen = 0 + $decoded = @() + + foreach ($byte in $Sequence) { + $onesCount = [System.Numerics.BitOperations]::PopCount([uint32]$byte) + if ($onesCount -band 1 -eq 1) + { + throw "wrong parity" + } + $sevenBits = $byte -shr 1 + $buffer = $buffer -shl 7 -bor $sevenBits + $bufferLen += 7 + while ($bufferLen -ge 8) + { + $shift = $bufferLen - 8 + $originalByte = $buffer -shr $shift -band 0xff + $bufferLen -= 8 + $decoded += $originalByte + } + } + $decoded +} diff --git a/exercises/practice/intergalactic-transmission/.meta/config.json b/exercises/practice/intergalactic-transmission/.meta/config.json new file mode 100644 index 0000000..186f91e --- /dev/null +++ b/exercises/practice/intergalactic-transmission/.meta/config.json @@ -0,0 +1,19 @@ +{ + "authors": [ + "glaxxie" + ], + "files": { + "solution": [ + "IntergalacticTransmission.ps1" + ], + "test": [ + "IntergalacticTransmission.tests.ps1" + ], + "example": [ + ".meta/IntergalacticTransmission.example.ps1" + ] + }, + "blurb": "Add parity bits to a message for transmission", + "source": "Kah Goh", + "source_url": "https://github.com/exercism/problem-specifications/pull/2543" +} diff --git a/exercises/practice/intergalactic-transmission/.meta/tests.toml b/exercises/practice/intergalactic-transmission/.meta/tests.toml new file mode 100644 index 0000000..64a8aac --- /dev/null +++ b/exercises/practice/intergalactic-transmission/.meta/tests.toml @@ -0,0 +1,88 @@ +# This is an auto-generated file. +# +# Regenerating this file via `configlet sync` will: +# - Recreate every `description` key/value pair +# - Recreate every `reimplements` key/value pair, where they exist in problem-specifications +# - Remove any `include = true` key/value pair (an omitted `include` key implies inclusion) +# - Preserve any other key/value pair +# +# As user-added comments (using the # character) will be removed when this file +# is regenerated, comments can be added via a `comment` key. + +[f99d4046-b429-4582-9324-f0bcac7ab51c] +description = "calculate transmit sequences -> empty message" + +[ee27ea2d-8999-4f23-9275-8f6879545f86] +description = "calculate transmit sequences -> 0x00 is transmitted as 0x0000" + +[97f27f98-8020-402d-be85-f21ba54a6df0] +description = "calculate transmit sequences -> 0x02 is transmitted as 0x0300" + +[24712fb9-0336-4e2f-835e-d2350f29c420] +description = "calculate transmit sequences -> 0x06 is transmitted as 0x0600" + +[7630b5a9-dba1-4178-b2a0-4a376f7414e0] +description = "calculate transmit sequences -> 0x05 is transmitted as 0x0581" + +[ab4fe80b-ef8e-4a99-b4fb-001937af415d] +description = "calculate transmit sequences -> 0x29 is transmitted as 0x2881" + +[4e200d84-593b-4449-b7c0-4de1b6a0955e] +description = "calculate transmit sequences -> 0xc001c0de is transmitted as 0xc000711be1" + +[fbc537e9-6b21-4f4a-8c2b-9cf9b702a9b7] +description = "calculate transmit sequences -> six byte message" + +[d5b75adf-b5fc-4f77-b4ab-77653e30f07c] +description = "calculate transmit sequences -> seven byte message" + +[6d8b297b-da1d-435e-bcd7-55fbb1400e73] +description = "calculate transmit sequences -> eight byte message" + +[54a0642a-d5aa-490c-be89-8e171a0cab6f] +description = "calculate transmit sequences -> twenty byte message" + +[9a8084dd-3336-474c-90cb-8a852524604d] +description = "decode received messages -> empty message" + +[879af739-0094-4736-9127-bd441b1ddbbf] +description = "decode received messages -> zero message" + +[7a89eeef-96c5-4329-a246-ec181a8e959a] +description = "decode received messages -> 0x0300 is decoded to 0x02" + +[3e515af7-8b62-417f-960c-3454bca7f806] +description = "decode received messages -> 0x0581 is decoded to 0x05" + +[a1b4a3f7-9f05-4b7a-b86e-d7c6fc3f16a9] +description = "decode received messages -> 0x2881 is decoded to 0x29" + +[2e99d617-4c91-4ad5-9217-e4b2447d6e4a] +description = "decode received messages -> first byte has wrong parity" + +[507e212d-3dae-42e8-88b4-2223838ff8d2] +description = "decode received messages -> second byte has wrong parity" + +[b985692e-6338-46c7-8cea-bc38996d4dfd] +description = "decode received messages -> 0xcf4b00 is decoded to 0xce94" + +[7a1f4d48-696d-4679-917c-21b7da3ff3fd] +description = "decode received messages -> 0xe2566500 is decoded to 0xe2ad90" + +[467549dc-a558-443b-80c5-ff3d4eb305d4] +description = "decode received messages -> six byte message" + +[1f3be5fb-093a-4661-9951-c1c4781c71ea] +description = "decode received messages -> seven byte message" + +[6065b8b3-9dcd-45c9-918c-b427cfdb28c1] +description = "decode received messages -> last byte has wrong parity" + +[98af97b7-9cca-4c4c-9de3-f70e227a4cb1] +description = "decode received messages -> eight byte message" + +[aa7d4785-2bb9-43a4-a38a-203325c464fb] +description = "decode received messages -> twenty byte message" + +[4c86e034-b066-42ac-8497-48f9bc1723c1] +description = "decode received messages -> wrong parity on 16th byte" diff --git a/exercises/practice/intergalactic-transmission/IntergalacticTransmission.ps1 b/exercises/practice/intergalactic-transmission/IntergalacticTransmission.ps1 new file mode 100644 index 0000000..03cb384 --- /dev/null +++ b/exercises/practice/intergalactic-transmission/IntergalacticTransmission.ps1 @@ -0,0 +1,43 @@ +Function Invoke-Transmitter() { + <# + .SYNOPSIS + Implement the transmitter to calculates the transmission sequence. + + .DESCRIPTION + Implement a function that accept a sequence and encode it with parity bits to help detecting transmission errors. + + .PARAMETER Sequence + An array of hexadecimal values. + + .EXAMPLE + Invoke-Transmitter -Sequence @(0x05) + Returns: @(0x05, 0x81) + #> + [CmdletBinding()] + Param( + [byte[]]$Sequence + ) + Throw "Please implement this function" +} + +Function Invoke-Receiver() { + <# + .SYNOPSIS + Implement the receiver to decode the transmission sequence. + + .DESCRIPTION + Implement a function to receive a sequence and decode it to the original message. + + .PARAMETER Sequence + An array of hexadecimal values. + + .EXAMPLE + Invoke-Receiver -Sequence @(0x05, 0x81) + Returns: @(0x05) + #> + [CmdletBinding()] + Param( + [byte[]]$Sequence + ) + Throw "Please implement this function" +} diff --git a/exercises/practice/intergalactic-transmission/IntergalacticTransmission.tests.ps1 b/exercises/practice/intergalactic-transmission/IntergalacticTransmission.tests.ps1 new file mode 100644 index 0000000..4d24713 --- /dev/null +++ b/exercises/practice/intergalactic-transmission/IntergalacticTransmission.tests.ps1 @@ -0,0 +1,197 @@ +BeforeAll { + . "./IntergalacticTransmission.ps1" +} + +Describe "IntergalacticTransmission test cases" { + Context "Calculate transmit sequences" { + It "empty message" { + $got = Invoke-Transmitter -Sequence @() + $expected = @() + + $got | Should -Be $expected + } + + It "0x00 is transmitted as 0x0000" { + $got = Invoke-Transmitter -Sequence @(0x00) + $expected = @(0x00, 0x00) + + $got | Should -Be $expected + } + + It "0x02 is transmitted as 0x0300" { + $got = Invoke-Transmitter -Sequence @(0x02) + $expected = @(0x03, 0x00) + + $got | Should -Be $expected + } + + It "0x06 is transmitted as 0x0600" { + $got = Invoke-Transmitter -Sequence @(0x06) + $expected = @(0x06, 0x00) + + $got | Should -Be $expected + } + + It "0x05 is transmitted as 0x0581" { + $got = Invoke-Transmitter -Sequence @(0x05) + $expected = @(0x05, 0x81) + + $got | Should -Be $expected + } + + It "0x29 is transmitted as 0x2881" { + $got = Invoke-Transmitter -Sequence @(0x29) + $expected = @(0x28, 0x81) + + $got | Should -Be $expected + } + + It "0xc001c0de is transmitted as 0xc000711be1" { + $got = Invoke-Transmitter -Sequence @(0xc0, 0x01, 0xc0, 0xde) + $expected = @(0xc0, 0x00, 0x71, 0x1b, 0xe1) + + $got | Should -Be $expected + } + + It "six byte message" { + $got = Invoke-Transmitter -Sequence @(0x47, 0x72, 0x65, 0x61, 0x74, 0x21) + $expected = @(0x47, 0xb8, 0x99, 0xac, 0x17, 0xa0, 0x84) + + $got | Should -Be $expected + } + + It "seven byte message" { + $got = Invoke-Transmitter -Sequence @(0x47, 0x72, 0x65, 0x61, 0x74, 0x31, 0x21) + $expected = @(0x47, 0xb8, 0x99, 0xac, 0x17, 0xa0, 0xc5, 0x42) + + $got | Should -Be $expected + } + + It "eight byte message" { + $got = Invoke-Transmitter -Sequence @(0xc0, 0x01, 0x13, 0x37, 0xc0, 0xde, 0x21, 0x21) + $expected = @(0xc0, 0x00, 0x44, 0x66, 0x7d, 0x06, 0x78, 0x42, 0x21, 0x81) + + $got | Should -Be $expected + } + + It "twenty byte message" { + $got = Invoke-Transmitter -Sequence @( + 0x45, 0x78, 0x65, 0x72, 0x63, 0x69, 0x73, 0x6d, 0x20, 0x69, + 0x73, 0x20, 0x61, 0x77, 0x65, 0x73, 0x6f, 0x6d, 0x65, 0x21 + ) + $expected = @( + 0x44, 0xbd, 0x18, 0xaf, 0x27, 0x1b, 0xa5, 0xe7, 0x6c, 0x90, + 0x1b, 0x2e, 0x33, 0x03, 0x84, 0xee, 0x65, 0xb8, 0xdb, 0xed, + 0xd7, 0x28, 0x84 + ) + + $got | Should -Be $expected + } + } + + Context "Decode received messages" { + It "empty message" { + $got = Invoke-Receiver -Sequence @() + $expected = @() + + $got | Should -Be $expected + } + + It "zero message" { + $got = Invoke-Receiver -Sequence @(0x00, 0x00) + $expected = @(0x00) + + $got | Should -Be $expected + } + + It "0x0300 is decoded to 0x02" { + $got = Invoke-Receiver -Sequence @(0x03, 0x00) + $expected = @(0x02) + + $got | Should -Be $expected + } + + It "0x0581 is decoded to 0x05" { + $got = Invoke-Receiver -Sequence @(0x05, 0x81) + $expected = @(0x05) + + $got | Should -Be $expected + } + + It "0x2881 is decoded to 0x29" { + $got = Invoke-Receiver -Sequence @(0x28, 0x81) + $expected = @(0x29) + + $got | Should -Be $expected + } + + It "first byte has wrong parity" { + { Invoke-Receiver -Sequence @(0x07, 0x00) } | Should -Throw "*wrong parity*" + } + + It "second byte has wrong parity" { + { Invoke-Receiver -Sequence @(0x03, 0x68) } | Should -Throw "*wrong parity*" + } + + It "0xcf4b00 is decoded to 0xce94" { + $got = Invoke-Receiver -Sequence @(0xcf, 0x4b, 0x00) + $expected = @(0xce, 0x94) + + $got | Should -Be $expected + } + + It "0xe2566500 is decoded to 0xe2ad90" { + $got = Invoke-Receiver -Sequence @(0xe2, 0x56, 0x65, 0x00) + $expected = @(0xe2, 0xad, 0x90) + + $got | Should -Be $expected + } + + It "six byte message" { + $got = Invoke-Receiver -Sequence @(0x47, 0xb8, 0x99, 0xac, 0x17, 0xa0, 0x84) + $expected = @(0x47, 0x72, 0x65, 0x61, 0x74, 0x21) + + $got | Should -Be $expected + } + + It "seven byte message" { + $got = Invoke-Receiver -Sequence @(0x47, 0xb8, 0x99, 0xac, 0x17, 0xa0, 0xc5, 0x42) + $expected = @(0x47, 0x72, 0x65, 0x61, 0x74, 0x31, 0x21) + + $got | Should -Be $expected + } + + It "last byte has wrong parity" { + { Invoke-Receiver -Sequence @(0x47, 0xb8, 0x99, 0xac, 0x17, 0xa0, 0xc5, 0x43) } | Should -Throw "*wrong parity*" + } + + It "eight byte message" { + $got = Invoke-Receiver -Sequence @(0xc0, 0x00, 0x44, 0x66, 0x7d, 0x06, 0x78, 0x42, 0x21, 0x81) + $expected = @(0xc0, 0x01, 0x13, 0x37, 0xc0, 0xde, 0x21, 0x21) + + $got | Should -Be $expected + } + + It "twenty byte message" { + $got = Invoke-Receiver -Sequence @( + 0x44, 0xbd, 0x18, 0xaf, 0x27, 0x1b, 0xa5, 0xe7, 0x6c, 0x90, + 0x1b, 0x2e, 0x33, 0x03, 0x84, 0xee, 0x65, 0xb8, 0xdb, 0xed, + 0xd7, 0x28, 0x84 + ) + $expected = @( + 0x45, 0x78, 0x65, 0x72, 0x63, 0x69, 0x73, 0x6d, 0x20, 0x69, + 0x73, 0x20, 0x61, 0x77, 0x65, 0x73, 0x6f, 0x6d, 0x65, 0x21 + ) + + $got | Should -Be $expected + } + + It "wrong parity on 16th byte" { + { Invoke-Receiver -Sequence @( + 0x44, 0xbd, 0x18, 0xaf, 0x27, 0x1b, 0xa5, 0xe7, 0x6c, 0x90, + 0x1b, 0x2e, 0x33, 0x03, 0x84, 0xef, 0x65, 0xb8, 0xdb, 0xed, + 0xd7, 0x28, 0x84 + ) } | Should -Throw "*wrong parity*" + } + } +}