* add practice exercise: transpose

config.json

@@ -402,6 +402,14 @@
         "prerequisites": [],
         "difficulty": 8
       },
+      {
+        "slug": "transpose",
+        "name": "Transpose",
+        "uuid": "501d8d8b-4dd9-457d-866f-88120f046277",
+        "practices": [],
+        "prerequisites": [],
+        "difficulty": 8
+      },
       {
         "slug": "word-count",
         "name": "Word Count",

exercises/practice/transpose/.docs/instructions.md

@@ -0,0 +1,61 @@
+# Instructions
+
+Given an input text output it transposed.
+
+Roughly explained, the transpose of a matrix:
+
+```text
+ABC
+DEF
+```
+
+is given by:
+
+```text
+AD
+BE
+CF
+```
+
+Rows become columns and columns become rows.
+See [transpose][].
+
+If the input has rows of different lengths, this is to be solved as follows:
+
+- Pad to the left with spaces.
+- Don't pad to the right.
+
+Therefore, transposing this matrix:
+
+```text
+ABC
+DE
+```
+
+results in:
+
+```text
+AD
+BE
+C
+```
+
+And transposing:
+
+```text
+AB
+DEF
+```
+
+results in:
+
+```text
+AD
+BE
+ F
+```
+
+In general, all characters from the input should also be present in the transposed output.
+That means that if a column in the input text contains only spaces on its bottom-most row(s), the corresponding output row should contain the spaces in its right-most column(s).
+
+[transpose]: https://en.wikipedia.org/wiki/Transpose

exercises/practice/transpose/.meta/config.json

@@ -0,0 +1,19 @@
+{
+  "authors": [
+    "jimmytty"
+  ],
+  "files": {
+    "solution": [
+      "transpose.sql"
+    ],
+    "test": [
+      "transpose_test.sql"
+    ],
+    "example": [
+      ".meta/example.sql"
+    ]
+  },
+  "blurb": "Take input text and output it transposed.",
+  "source": "Reddit r/dailyprogrammer challenge #270 [Easy].",
+  "source_url": "https://web.archive.org/web/20230630051421/https://old.reddit.com/r/dailyprogrammer/comments/4msu2x/challenge_270_easy_transpose_the_input_text/"
+}

exercises/practice/transpose/.meta/example.sql

@@ -0,0 +1,63 @@
+DROP TABLE IF EXISTS jmatrix;
+CREATE TEMPORARY TABLE jmatrix AS
+SELECT lines,
+  (
+    WITH to_line (line) AS (
+      WITH RECURSIVE split_lines (string, line) AS (
+        VALUES (REPLACE(lines, ' ', CHAR(7))||CHAR(10), NULL)
+        UNION ALL
+        SELECT SUBSTR(string, INSTR(string, CHAR(10)) + 1),
+               SUBSTR(string, 1, INSTR(string, CHAR(10)) - 1)
+          FROM split_lines
+         WHERE string <> ''
+      )
+      SELECT line FROM split_lines WHERE line NOTNULL
+    )
+    SELECT JSON_GROUP_ARRAY(
+      (
+        WITH RECURSIVE to_letter (string, letter) AS (
+          VALUES (
+            PRINTF('%-*s', (SELECT MAX(LENGTH(line)) FROM to_line), line),
+            NULL
+          )
+          UNION ALL
+          SELECT SUBSTR(string, 2), SUBSTR(string, 1, 1)
+            FROM to_letter
+           WHERE string <> ''
+        )
+        SELECT JSON_GROUP_ARRAY(letter)
+          FROM to_letter
+         WHERE letter NOTNULL
+      )
+    ) AS matrix
+      FROM to_line
+  ) AS matrix
+  FROM transpose
+;
+
+UPDATE transpose SET result = '' WHERE lines = '';
+
+UPDATE transpose
+   SET result = (
+     WITH RECURSIVE to_transpose (jarray, idx, ncols, new_row) AS (
+       VALUES (
+         jmatrix.matrix,
+         0,
+         JSON_ARRAY_LENGTH(JSON_EXTRACT(jmatrix.matrix, '$[0]')),
+         NULL
+       )
+       UNION ALL
+       SELECT jarray, idx + 1, ncols, (
+         SELECT GROUP_CONCAT(JSON_EXTRACT(j.value, PRINTF('$[%d]', idx)), '')
+           FROM JSON_EACH(jarray) j
+       )
+         FROM to_transpose
+        WHERE idx < ncols
+     )
+     SELECT GROUP_CONCAT(REPLACE(RTRIM(new_row,' '), CHAR(7), ' '), CHAR(10))
+       FROM to_transpose
+   )
+  FROM jmatrix
+ WHERE transpose.lines = jmatrix.lines
+   AND result ISNULL
+;

exercises/practice/transpose/.meta/tests.toml

@@ -0,0 +1,46 @@
+# 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.
+
+[404b7262-c050-4df0-a2a2-0cb06cd6a821]
+description = "empty string"
+
+[a89ce8a3-c940-4703-a688-3ea39412fbcb]
+description = "two characters in a row"
+
+[855bb6ae-4180-457c-abd0-ce489803ce98]
+description = "two characters in a column"
+
+[5ceda1c0-f940-441c-a244-0ced197769c8]
+description = "simple"
+
+[a54675dd-ae7d-4a58-a9c4-0c20e99a7c1f]
+description = "single line"
+
+[0dc2ec0b-549d-4047-aeeb-8029fec8d5c5]
+description = "first line longer than second line"
+
+[984e2ec3-b3d3-4b53-8bd6-96f5ef404102]
+description = "second line longer than first line"
+
+[eccd3784-45f0-4a3f-865a-360cb323d314]
+description = "mixed line length"
+
+[85b96b3f-d00c-4f80-8ca2-c8a5c9216c2d]
+description = "square"
+
+[b9257625-7a53-4748-8863-e08e9d27071d]
+description = "rectangle"
+
+[b80badc9-057e-4543-bd07-ce1296a1ea2c]
+description = "triangle"
+
+[76acfd50-5596-4d05-89f1-5116328a7dd9]
+description = "jagged triangle"

exercises/practice/transpose/create_fixture.sql

@@ -0,0 +1,11 @@
+DROP TABLE IF EXISTS transpose;
+CREATE TABLE transpose (
+    lines  TEXT NOT NULL,
+    result TEXT
+);
+
+.mode csv
+.import ./data.csv transpose
+
+UPDATE transpose SET result = NULL;
+UPDATE transpose SET lines = REPLACE(lines, '\n', CHAR(10));

exercises/practice/transpose/create_test_table.sql

@@ -0,0 +1,34 @@
+DROP TABLE IF EXISTS tests;
+CREATE TABLE IF NOT EXISTS tests (
+    -- uuid and description are taken from the test.toml file
+    uuid TEXT PRIMARY KEY,
+    description TEXT NOT NULL,
+    -- The following section is needed by the online test-runner
+    status TEXT DEFAULT 'fail',
+    message TEXT,
+    output TEXT,
+    test_code TEXT,
+    task_id INTEGER DEFAULT NULL,
+    -- Here are columns for the actual tests
+    lines TEXT NOT NULL,
+    expected TEXT NOT NULL
+);
+
+INSERT INTO tests (uuid, description, lines, expected)
+VALUES
+        ('404b7262-c050-4df0-a2a2-0cb06cd6a821', 'empty string', '', ''),
+        ('a89ce8a3-c940-4703-a688-3ea39412fbcb', 'two characters in a row', 'A1', 'A\n1'),
+        ('855bb6ae-4180-457c-abd0-ce489803ce98', 'two characters in a column', 'A\n1', 'A1'),
+        ('5ceda1c0-f940-441c-a244-0ced197769c8', 'simple', 'ABC\n123', 'A1\nB2\nC3'),
+        ('a54675dd-ae7d-4a58-a9c4-0c20e99a7c1f', 'single line', 'Single line.', 'S\ni\nn\ng\nl\ne\n \nl\ni\nn\ne\n.'),
+        ('0dc2ec0b-549d-4047-aeeb-8029fec8d5c5', 'first line longer than second line', 'The fourth line.\nThe fifth line.', 'TT\nhh\nee\n  \nff\noi\nuf\nrt\nth\nh \n l\nli\nin\nne\ne.\n.'),
+        ('984e2ec3-b3d3-4b53-8bd6-96f5ef404102', 'second line longer than first line', 'The first line.\nThe second line.', 'TT\nhh\nee\n  \nfs\nie\nrc\nso\ntn\n d\nl \nil\nni\nen\n.e\n .'),
+        ('eccd3784-45f0-4a3f-865a-360cb323d314', 'mixed line length', 'The longest line.\nA long line.\nA longer line.\nA line.', 'TAAA\nh   \nelll\n ooi\nlnnn\nogge\nn e.\nglr\nei \nsnl\ntei\n .n\nl e\ni .\nn\ne\n.'),
+        ('85b96b3f-d00c-4f80-8ca2-c8a5c9216c2d', 'square', 'HEART\nEMBER\nABUSE\nRESIN\nTREND', 'HEART\nEMBER\nABUSE\nRESIN\nTREND'),
+        ('b9257625-7a53-4748-8863-e08e9d27071d', 'rectangle', 'FRACTURE\nOUTLINED\nBLOOMING\nSEPTETTE', 'FOBS\nRULE\nATOP\nCLOT\nTIME\nUNIT\nRENT\nEDGE'),
+        ('b80badc9-057e-4543-bd07-ce1296a1ea2c', 'triangle', 'T\nEE\nAAA\nSSSS\nEEEEE\nRRRRRR', 'TEASER\n EASER\n  ASER\n   SER\n    ER\n     R'),
+        ('76acfd50-5596-4d05-89f1-5116328a7dd9', 'jagged triangle', '11\n2\n3333\n444\n555555\n66666', '123456\n1 3456\n  3456\n  3 56\n    56\n    5');
+
+UPDATE tests
+   SET lines = REPLACE(lines, '\n', CHAR(10)),
+       expected = REPLACE(expected, '\n', CHAR(10));

exercises/practice/transpose/data.csv

@@ -0,0 +1,12 @@
+"",
+"A1",
+"A\n1",
+"ABC\n123",
+"Single line.",
+"The fourth line.\nThe fifth line.",
+"The first line.\nThe second line.",
+"The longest line.\nA long line.\nA longer line.\nA line.",
+"HEART\nEMBER\nABUSE\nRESIN\nTREND",
+"FRACTURE\nOUTLINED\nBLOOMING\nSEPTETTE",
+"T\nEE\nAAA\nSSSS\nEEEEE\nRRRRRR",
+"11\n2\n3333\n444\n555555\n66666",

exercises/practice/transpose/transpose.sql

@@ -0,0 +1,7 @@
+-- Schema:
+-- CREATE TABLE transpose (
+--     lines  TEXT NOT NULL,
+--     result TEXT
+-- );
+--
+-- Task: update the transpose table and set the result based on the lines.

exercises/practice/transpose/transpose_test.sql

@@ -0,0 +1,40 @@
+-- Create database:
+.read ./create_fixture.sql
+
+-- Read user student solution and save any output as markdown in user_output.md:
+.mode markdown
+.output user_output.md
+.read ./transpose.sql
+.output
+
+-- Create a clean testing environment:
+.read ./create_test_table.sql
+
+-- Comparison of user input and the tests updates the status for each test:
+UPDATE tests
+SET status = 'pass'
+FROM (SELECT lines, result FROM transpose) AS actual
+WHERE (actual.lines, actual.result) = (tests.lines, tests.expected);
+
+-- Update message for failed tests to give helpful information:
+UPDATE tests
+SET message = (
+    'Result for "'
+    || tests.lines
+    || '"'
+    || ' is <' || COALESCE(actual.result, 'NULL')
+    || '> but should be <' || tests.expected || '>'
+)
+FROM (SELECT lines, result FROM transpose) AS actual
+WHERE actual.lines = tests.lines AND tests.status = 'fail';
+
+-- Save results to ./output.json (needed by the online test-runner)
+.mode json
+.once './output.json'
+SELECT description, status, message, output, test_code, task_id
+FROM tests;
+
+-- Display test results in readable form for the student:
+.mode table
+SELECT description, status, message
+FROM tests;