Add readme describing repo and how to run tests

13_prime_sieve.lua

@@ -1,43 +0,0 @@
--- Write a function which takes a limit and returns a list of every
--- prime number below that limit.  It is recommended that you use the
--- "Sieve of Eratosthenes" algorithm, but you can try a different
--- prime sieve algorithm if you want.
---
--- Solution --------------------------------------------------------------------
-function lesser_primes(limit)
-	-- Your implementation here
-end
-
--- Tests -----------------------------------------------------------------------
-
-local luaunit = require("luaunit.luaunit")
-
-function test_primes_below_2048()
-	local primes = {
-		2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71,
-		73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151,
-		157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233,
-		239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317,
-		331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419,
-		421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503,
-		509, 521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607,
-		613, 617, 619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701,
-		709, 719, 727, 733, 739, 743, 751, 757, 761, 769, 773, 787, 797, 809, 811,
-		821, 823, 827, 829, 839, 853, 857, 859, 863, 877, 881, 883, 887, 907, 911,
-		919, 929, 937, 941, 947, 953, 967, 971, 977, 983, 991, 997, 1009, 1013, 1019,
-		1021, 1031, 1033, 1039, 1049, 1051, 1061, 1063, 1069, 1087, 1091, 1093, 1097,
-		1103, 1109, 1117, 1123, 1129, 1151, 1153, 1163, 1171, 1181, 1187, 1193, 1201,
-		1213, 1217, 1223, 1229, 1231, 1237, 1249, 1259, 1277, 1279, 1283, 1289, 1291,
-		1297, 1301, 1303, 1307, 1319, 1321, 1327, 1361, 1367, 1373, 1381, 1399, 1409,
-		1423, 1427, 1429, 1433, 1439, 1447, 1451, 1453, 1459, 1471, 1481, 1483, 1487,
-		1489, 1493, 1499, 1511, 1523, 1531, 1543, 1549, 1553, 1559, 1567, 1571, 1579,
-		1583, 1597, 1601, 1607, 1609, 1613, 1619, 1621, 1627, 1637, 1657, 1663, 1667,
-		1669, 1693, 1697, 1699, 1709, 1721, 1723, 1733, 1741, 1747, 1753, 1759, 1777,
-		1783, 1787, 1789, 1801, 1811, 1823, 1831, 1847, 1861, 1867, 1871, 1873, 1877,
-		1879, 1889, 1901, 1907, 1913, 1931, 1933, 1949, 1951, 1973, 1979, 1987, 1993,
-		1997, 1999, 2003, 2011, 2017, 2027, 2029, 2039
-	}
-	luaunit.assertEquals(lesser_primes(2048), primes)
-end
-
-os.exit(luaunit.LuaUnit.run())

14_vigenere.lua

@@ -1,64 +0,0 @@
--- The Vigenère cipher is a way to encrypt text, where a key is
--- repeated for the length of the plaintext and the alphabetical
--- position of the keyword letter determines the amount the letter of
--- the plaintext is shifted by.  For example, for plaintext "FOO" and
--- key "BAR", the first letter of the cipher text would be G, the
--- result of shifting the letter F (first letter of the plaintext)
--- over by 1 (the zero-based alphabetical position of B, first letter
--- of the key).
---
--- Implement a function to encode a message with a given keyword.  The
--- message should be converted to upper-case and any non-alphabetical
--- characters should be discarded.
---
--- Solution --------------------------------------------------------------------
-local a_value = 65
-
-function apply_shift(letter, shift)
-	local shifted = (letter - a_value + shift) % 26
-	return a_value + shifted
-end
-
-function vigenere_encode(plaintext, keyword)
-	local key = {}
-	for i = 1, #keyword do
-		local shift = string.byte(keyword, i) - a_value
-		table.insert(key, shift)
-	end
-
-	plaintext = string.gsub(string.upper(plaintext), "%A+", "")
-	ciphertext = ""
-	for i = 1, #plaintext do
-		local letter = string.byte(plaintext, i)
-		local shift = key[(i - 1) % #key + 1]
-		local shifted = apply_shift(letter, shift)
-		ciphertext = ciphertext .. string.char(shifted)
-	end
-
-	return ciphertext
-end
-
--- Tests -----------------------------------------------------------------------
-
-local luaunit = require("luaunit.luaunit")
-
-function test_encoding_of_foo_with_key_BAR()
-	luaunit.assertEquals(vigenere_encode("FOO", "BAR"), "GOF")
-end
-
-function test_encoding_of_the_quick_brown_fox_with_key_JUMPSOVER()
-	local plaintext = "The quick brown fox"
-	local key = "JUMPSOVER"
-	local expected = "CBQFMWXOSAIICXCS"
-	luaunit.assertEquals(vigenere_encode(plaintext, key), expected)
-end
-
-function test_encoding_longer_phrase_with_key_LEAR()
-	local plaintext =
-		"They dined on mince and slices of quince, which they ate with a runcible spoon."
-	local key = "LEAR"
-	local expected = "ELEPOMNVOSNDTRCVLRDJWMCVDSFHFMNTPAHZNLTYPCAKPAIKSERLYGISWISGZSN"
-	luaunit.assertEquals(vigenere_encode(plaintext, key), expected)
-end
-
-os.exit(luaunit.LuaUnit.run())

15_run_length_encoding.lua

@@ -1,28 +0,0 @@
--- Run length encoding is a simple data compression technique where a
--- "run" of the same value is replaced with a count and a single copy.
--- In this exercise we will use the notation "#<count>:<value>" to
--- indicate such a run; however, this should only be put into the
--- output if it is strictly shorter than the string it is replacing.
--- The input will consist only of alphanumeric characters.
---
--- Solution --------------------------------------------------------------------
-function run_length_encode(input)
-	-- Your implementation here
-end
--- Tests -----------------------------------------------------------------------
-
-local luaunit = require("luaunit.luaunit")
-
-function test_encoding_of_aaaaaaaa22bbbbbbssssfffffff67eee66666asdfff()
-	local input = "aaaaaaaa22bbbbbbssssfffffff67eee66666asdfff"
-	local expected = "#8:a22#6:bssss#7:f67eee#5:6asdfff"
-	luaunit.assertEquals(run_length_encode(input), expected)
-end
-
-function test_encoding_of_wwwwwfffff1223566666666bbbbbbbbbbb78b99asasdfbnfasdafffffff99()
-	local input = "wwwwwfffff1223566666666bbbbbbbbbbb78b99asasdfbnfasdafffffff99"
-	local expected = "#5:w#5:f12235#8:6#11:b78b99asasdfbnfasda#7:f99"
-	luaunit.assertEquals(run_length_encode(input), expected)
-end
-
-os.exit(luaunit.LuaUnit.run())

16_postfix.lua

@@ -1,47 +0,0 @@
--- Postfix notation is an alternative to the normal "infix" notation
--- used in mathematical expressions.  Instead of writing the operator
--- between the operands, the operator comes after them.  For example,
--- "1 + 2" is notated as "1 2 +".  This removes the need for operator
--- precedence and parentheses: rather than having to resolve the
--- ambiguity of an expression like "1 + 2 * 3" with convention or
--- parentheses, the evaluation order is explicit -- multiplication-
--- first is "1 2 3 * +" and addition-first is "1 2 + 3 *".
---
--- As well as this notational convenience, postfix can be easily
--- evaluated using a stack.  Whenever an operand is encountered, the
--- value is pushed onto the stack, and whenever an operator is
--- encountered, two values are popped from the stack and the result of
--- the operation is pushed on in their place.  Finally, the value left
--- on the top of the stack is the result of the operation.
---
--- Write a function that will evaluate a postfix expression and return
--- the result.  You can assume that the expression is valid, and not
--- worry about handling error cases.  The operators will be "+", "-",
--- "*" and "/".
---
--- Solution --------------------------------------------------------------------
-function evaluate_postfix(expression)
-	-- Your implementation here
-end
-
--- Tests -----------------------------------------------------------------------
-
-local luaunit = require("luaunit.luaunit")
-
-function test_1_2_plus_3_times_is_9()
-	luaunit.assertEquals(evaluate_postfix("1 2 + 3 *"), 9)
-end
-
-function test_1_2_3_times_plus_is_7()
-	luaunit.assertEquals(evaluate_postfix("1 2 3 * +"), 7)
-end
-
-function test_4_6_plus_5_divide_2_1_minus_minus_is_1()
-	luaunit.assertEquals(evaluate_postfix("4 6 + 5 / 2 1 - -"), 1)
-end
-
-function test_12_2_times_6_divide_10_times_2_plus_is_42()
-	luaunit.assertEquals(evaluate_postfix("12 2 * 6 / 10 * 2 +"), 42)
-end
-
-os.exit(luaunit.LuaUnit.run())

17_prime_factors.lua

@@ -1,50 +0,0 @@
--- Write a function which determines the prime factors of a given
--- number, returning them in a list.  You may assume that none of the
--- prime factors are above 10000
---
--- Solution --------------------------------------------------------------------
-function prime_factors(n)
-	-- Your implementation here
-end
-
--- Tests -----------------------------------------------------------------------
-
-local luaunit = require("luaunit.luaunit")
-
-function test_prime_factors_of_42()
-	luaunit.assertItemsEquals(prime_factors(42), {2, 3, 7})
-end
-
-function test_prime_factors_of_70()
-	luaunit.assertItemsEquals(prime_factors(70), {2, 5, 7})
-end
-
-function test_prime_factors_of_253()
-	luaunit.assertItemsEquals(prime_factors(253), {11, 23})
-end
-
-function test_prime_factors_of_245()
-	luaunit.assertItemsEquals(prime_factors(245), {5, 7, 7})
-end
-
-function test_prime_factors_of_36()
-	luaunit.assertItemsEquals(prime_factors(36), {2, 2, 3, 3})
-end
-
-function test_prime_factors_of_1337()
-	luaunit.assertItemsEquals(prime_factors(1337), {7, 191})
-end
-
-function test_prime_factors_of_4321()
-	luaunit.assertItemsEquals(prime_factors(4321), {29, 149})
-end
-
-function test_prime_factors_of_57812834()
-	luaunit.assertItemsEquals(prime_factors(57812834), {2, 29, 113, 8821})
-end
-
-function test_prime_factors_of_8894220()
-	luaunit.assertItemsEquals(prime_factors(8894220), {2, 2, 3, 5, 271, 547})
-end
-
-os.exit(luaunit.LuaUnit.run())

18_towers_of_hanoi.lua

@@ -1,81 +0,0 @@
--- The Towers of Hanoi is a mathematical puzzle consisting of three
--- rods and a number of disks of various diameters which can slide
--- onto any rod.  Initially, all the disks are stacked in decreasing
--- size order so that they form a conical shape.  The objective to
--- move the entire stack to one of the other two rods, with each move
--- consisting of taking the uppermost disk from one of the rods and
--- placing it on top of the stack on another one.  A disk cannot be
--- placed on top of a disk of smaller diameter.
---
--- Write a function which generates an optimal solution to the puzzle.
--- The rods are numbered 1-3, with the stack starting on rod 1.  Your
--- function should return a list of {from = <rod>, to = <rod>} tables,
--- and will receive the number of disks in the original stack as its
--- argument.
---
--- Solution --------------------------------------------------------------------
-function towers_of_hanoi_solution(disk_count)
-	-- Your implementation here
-end
-
--- Tests -----------------------------------------------------------------------
-
-local luaunit = require("luaunit.luaunit")
-
-local function disk_stack(count)
-	local stack = {}
-	for i = count, 1, -1 do table.insert(stack, i) end
-	return stack
-end
-
-local function assert_valid(state)
-	for _, rod in ipairs(state) do
-		local previous = rod[1]
-		for _, disk in ipairs(rod) do
-			luaunit.assertTrue(disk <= previous)
-			previous = disk
-		end
-	end
-	return true
-end
-
-local function assert_solved(state, disk_count)
-	luaunit.assertEquals(state[1], {})
-	if #state[2] ~= 0 then
-		luaunit.assertEquals(state[2], disk_stack(disk_count))
-		luaunit.assertEquals(state[3], {})
-	else
-		luaunit.assertEquals(state[2], {})
-		luaunit.assertEquals(state[3], disk_stack(disk_count))
-	end
-end
-
-local function assert_is_solution(solution, disk_count)
-	local state = {disk_stack(disk_count), {}, {}}
-	for i, move in ipairs(solution) do
-		local disk = table.remove(state[move.from])
-		table.insert(state[move.to], disk)
-		assert_valid(state)
-	end
-	assert_solved(state, disk_count)
-end
-
-local function test_with_count(disk_count)
-	local solution = towers_of_hanoi_solution(disk_count)
-	assert_is_solution(solution, disk_count)
-	luaunit.assertEquals(#solution, 2 ^ disk_count - 1)
-end
-
-function test_with_1_disk()
-	test_with_count(1)
-end
-
-function test_with_7_disks()
-	test_with_count(7)
-end
-
-function test_with_12_disks()
-	test_with_count(12)
-end
-
-os.exit(luaunit.LuaUnit.run())

19_dependencies.lua

@@ -1,105 +0,0 @@
--- Write a function to generate a valid order for a number of jobs
--- that depend upon each other.  Your input is a jobs table; each key
--- is a job number, with its the values being a list jobs it depends
--- on.  You may assume that there are no circular dependencies.
---
--- Return a list of job numbers, so that performing the jobs in that
--- order ensures that all jobs are exactly once, and all dependencies
--- of a job are done before prior to it.
---
--- Solution --------------------------------------------------------------------
-function schedule(jobs)
-	-- Your implementation here
-end
-
--- Tests -----------------------------------------------------------------------
-
-local luaunit = require("luaunit.luaunit")
-
-local function keys(t)
-	local results = {}
-	for key, _ in pairs(t) do table.insert(results, key) end
-	return results
-end
-
-local function contains(list, target)
-	for _, item in ipairs(list) do if item == target then return true end end
-	return false
-end
-
-local function deep_copy(original)
-	local copy = {}
-	if type(original) == "table" then
-		for key, value in pairs(original) do
-			local key_copy = deep_copy(key)
-			local value_copy = deep_copy(value)
-			copy[key_copy] = value_copy
-		end
-	else
-		copy = original
-	end
-	return copy
-end
-
-local function assert_valid(order, jobs)
-	local done = {}
-	for _, job in ipairs(order) do
-		for _, dependency in ipairs(jobs[job]) do
-			luaunit.assertTrue(contains(done, dependency))
-		end
-		table.insert(done, job)
-	end
-end
-
-local function test_case(jobs)
-	local order = schedule(deep_copy(jobs))
-	luaunit.assertItemsEquals(order, keys(jobs))
-	assert_valid(order, jobs)
-end
-
-function test_sequential_dependencies()
-	local jobs = {[1] = {2}, [2] = {3}, [3] = {}}
-	test_case(jobs)
-end
-
-function test_converging_dependencies()
-	local jobs = {
-		[1] = {5},
-		[2] = {5},
-		[3] = {6},
-		[4] = {6},
-		[5] = {7},
-		[6] = {7},
-		[7] = {},
-	}
-	test_case(jobs)
-end
-
-function test_diverging_dependencies()
-	local jobs = {
-		[1] = {2, 3},
-		[2] = {4, 5},
-		[3] = {6, 7},
-		[4] = {},
-		[5] = {},
-		[6] = {},
-		[7] = {}
-	}
-	test_case(jobs)
-end
-
-function test_compound_dependencies()
-	local jobs = {
-		[1] = {2, 3, 4},
-		[2] = {5, 6},
-		[3] = {7},
-		[4] = {7},
-		[5] = {},
-		[6] = {8},
-		[7] = {8},
-		[8] = {}
-	}
-	test_case(jobs)
-end
-
-os.exit(luaunit.LuaUnit.run())

20_legal_captures.lua

@@ -1,340 +0,0 @@
--- Write a function which takes a description of a chess position and
--- returns a list of all legal captures from that position.
---
--- The position will be given as a table, containing the keys "turn",
--- indicating which player it is to move, "board", which will contain
--- a rank-major grid of pieces (that is, a list of ranks/rows).  Each
--- piece will be indicated by its unicode symbol.  The lack of a piece
--- will be indicated by nil.  If the previous move was a pawn moving
--- two places, the key "en_passant_target" will be set to a table with
--- "rank" and "file" keys set to the (1-based) rank and file indices
--- of the square passed over by the pawn.
---
--- For example, the starting position would be given as:
---
--- {
---     turn = "white",
---     board = {
---         {"♖", "♘", "♗", "♕", "♔", "♗", "♘", "♖"},
---         {"♙", "♙", "♙", "♙", "♙", "♙", "♙", "♙"},
---         {nil, nil, nil, nil, nil, nil, nil, nil},
---         {nil, nil, nil, nil, nil, nil, nil, nil},
---         {nil, nil, nil, nil, nil, nil, nil, nil},
---         {nil, nil, nil, nil, nil, nil, nil, nil},
---         {"♟︎", "♟︎", "♟︎", "♟︎", "♟︎", "♟︎", "♟︎", "♟︎"},
---         {"♜", "♞", "♝", "♛", "♚", "♝", "♞", "♜"},
---     },
--- }
---
--- Moves should be returned in figurine algebraic notation, without
--- indicators for en passant, check or checkmate (i.e. no "e.p.", "+"
--- or "#").  For example, "♞xc6" for a black night capturing on c6 and
--- "exd7" for an e-file pawn capturing on d7.  For the sake of
--- simplicity, there's no requirement to disambiguate between two
--- pieces of the same type when the notation for the capture would
--- otherwise be the same (e.g. if two rooks can capture on the same
--- square).  However, there should be duplicate entries in the results
--- list for each.
---
--- Solution --------------------------------------------------------------------
-function legal_captures(position)
-	-- Your implementation here
-end
-
--- Tests -----------------------------------------------------------------------
-
-local luaunit = require("luaunit.luaunit")
-
-function test_starting_position()
-	local position = {
-		turn = "white",
-		board = {
-			{"♖", "♘", "♗", "♕", "♔", "♗", "♘", "♖"},
-			{"♙", "♙", "♙", "♙", "♙", "♙", "♙", "♙"},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{"♟︎", "♟︎", "♟︎", "♟︎", "♟︎", "♟︎", "♟︎", "♟︎"},
-			{"♜", "♞", "♝", "♛", "♚", "♝", "♞", "♜"},
-		},
-	}
-	local expected = {}
-	luaunit.assertItemsEquals(legal_captures(position), expected)
-end
-
-function test_queens_gambit()
-	local position = {
-		turn = "black",
-		board = {
-			{"♖", "♘", "♗", "♕", "♔", "♗", "♘", "♖"},
-			{"♙", "♙", nil, nil, "♙", "♙", "♙", "♙"},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, "♙", "♙", nil, nil, nil, nil},
-			{nil, nil, nil, "♟︎", nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{"♟︎", "♟︎", "♟︎", nil, "♟︎", "♟︎", "♟︎", "♟︎"},
-			{"♜", "♞", "♝", "♛", "♚", "♝", "♞", "♜"},
-		},
-	}
-	local expected = {"dxc4"}
-	luaunit.assertItemsEquals(legal_captures(position), expected)
-end
-
-function test_scandinavian_defense()
-	local position = {
-		turn = "white",
-		board = {
-			{"♖", "♘", "♗", "♕", "♔", "♗", "♘", "♖"},
-			{"♙", "♙", "♙", "♙", nil, "♙", "♙", "♙"},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, "♙", nil, nil, nil},
-			{nil, nil, nil, "♟︎", nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{"♟︎", "♟︎", "♟︎", nil, "♟︎", "♟︎", "♟︎", "♟︎"},
-			{"♜", "♞", "♝", "♛", "♚", "♝", "♞", "♜"},
-		},
-	}
-	local expected = {"exd5"}
-	luaunit.assertItemsEquals(legal_captures(position), expected)
-end
-
-function test_knight_captures()
-	local position = {
-		turn = "black",
-		board = {
-			{"♙", "♙", "♙", "♙", "♙", "♙", "♙", "♙"},
-			{"♙", "♙", "♙", nil, "♙", "♙", "♙", "♙"},
-			{"♙", "♙", nil, nil, nil, "♙", "♙", "♙"},
-			{"♙", nil, nil, "♞", nil, nil, "♙", "♙"},
-			{"♙", "♙", nil, nil, nil, "♙", "♙", "♙"},
-			{"♙", "♙", "♙", nil, "♙", "♙", "♙", "♙"},
-			{"♙", "♙", "♙", "♙", "♙", "♙", "♙", "♙"},
-			{"♙", "♙", "♙", "♙", "♙", "♙", "♙", "♙"},
-		},
-	}
-	local expected = {
-		"♞xb3", "♞xb5", "♞xc2", "♞xc6", "♞xe2", "♞xe6", "♞xf3", "♞xf5",
-	}
-	luaunit.assertItemsEquals(legal_captures(position), expected)
-end
-
-function test_knight_not_blocked()
-	local position = {
-		turn = "white",
-		board = {
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, "♟︎", "♟︎", "♟︎", nil, nil},
-			{nil, nil, nil, nil, "♟︎", nil, nil, nil},
-			{nil, nil, "♟︎", "♟︎", "♘", nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-		},
-	}
-	local expected = {"♘xd3", "♘xf3"}
-	luaunit.assertItemsEquals(legal_captures(position), expected)
-end
-
-function test_bishop_captures()
-	local position = {
-		turn = "black",
-		board = {
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{"♙", nil, nil, nil, nil, nil, "♙", nil},
-			{nil, nil, nil, "♙", nil, nil, "♙", nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, "♙", "♝", nil, nil, nil, "♙"},
-			{nil, nil, nil, nil, "♙", nil, nil, nil},
-			{nil, "♙", nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, "♙", nil, nil, nil, nil},
-		},
-	}
-	local expected = {"♝xa2", "♝xb7", "♝xe6", "♝xg2"}
-	luaunit.assertItemsEquals(legal_captures(position), expected)
-end
-
-function test_bishop_blocked()
-	local position = {
-		turn = "black",
-		board = {
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, "♙", nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, "♞", nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, "♝", nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-		},
-	}
-	local expected = {}
-	luaunit.assertItemsEquals(legal_captures(position), expected)
-end
-
-function test_rook_captures()
-	local position = {
-		turn = "white",
-		board = {
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{"♟︎", nil, nil, nil, nil, nil, "♟︎", nil},
-			{nil, nil, nil, "♟︎", nil, nil, "♟︎", nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, "♟︎", "♖", nil, nil, nil, "♟︎"},
-			{nil, nil, nil, nil, "♟︎", nil, nil, nil},
-			{nil, "♟︎", nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, "♟︎", nil, nil, nil, nil},
-		},
-	}
-	local expected = {"♖xc5", "♖xd3", "♖xd8", "♖xh5"}
-	luaunit.assertItemsEquals(legal_captures(position), expected)
-end
-
-function test_rook_blocked()
-	local position = {
-		turn = "white",
-		board = {
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, "♖", "♙", nil, nil, nil, "♟︎", nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-		},
-	}
-	local expected = {}
-	luaunit.assertItemsEquals(legal_captures(position), expected)
-end
-
-function test_queen_captures()
-	local position = {
-		turn = "black",
-		board = {
-			{nil, "♙", "♙", "♙", "♙", "♙", nil, "♙"},
-			{"♙", "♙", "♙", nil, "♙", "♙", "♙", "♙"},
-			{"♙", "♙", nil, nil, nil, "♙", "♙", "♙"},
-			{"♙", nil, nil, "♛", nil, nil, "♙", nil},
-			{"♙", "♙", nil, nil, nil, "♙", "♙", "♙"},
-			{"♙", "♙", "♙", nil, "♙", "♙", "♙", "♙"},
-			{nil, "♙", "♙", "♙", "♙", "♙", nil, "♙"},
-			{"♙", "♙", "♙", nil, "♙", "♙", "♙", nil},
-		},
-	}
-	local expected = {
-		"♛xa4", "♛xb2", "♛xb6", "♛xd1", "♛xd7", "♛xf2", "♛xf6", "♛xg4",
-	}
-	luaunit.assertItemsEquals(legal_captures(position), expected)
-end
-
-function test_queen_blocked()
-	local position = {
-		turn = "white",
-		board = {
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, "♟︎", nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, "♙", nil, nil, nil, nil, nil},
-			{nil, "♕", "♙", nil, nil, nil, "♟︎", nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-		},
-	}
-	local expected = {}
-	luaunit.assertItemsEquals(legal_captures(position), expected)
-end
-
-function test_king_captures()
-	local position = {
-		turn = "black",
-		board = {
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, "♙", "♙", "♙", nil, nil, nil},
-			{nil, nil, "♙", "♚", "♙", nil, nil, nil},
-			{nil, nil, "♙", "♙", "♙", nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-		},
-	}
-	local expected = {"♚xc3","♚xc4","♚xc5","♚xd3","♚xd5","♚xe3","♚xe4","♚xe5",}
-	luaunit.assertItemsEquals(legal_captures(position), expected)
-end
-
-function test_en_passant()
-	local position = {
-		turn = "white",
-		board = {
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, "♟︎", "♙", nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-		},
-		en_passant_target = {rank = 6, file = 4},
-	}
-	local expected = {"exd6"}
-	luaunit.assertItemsEquals(legal_captures(position), expected)
-end
-
-function test_cannot_capture_if_leads_to_check()
-	local position = {
-		turn = "white",
-		board = {
-			{nil, nil, nil, nil, "♔", nil, nil, nil},
-			{nil, nil, nil, nil, "♗", nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, "♟︎", nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, "♜", nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-		},
-		en_passant_target = {rank = 6, file = 4},
-	}
-	local expected = {}
-	luaunit.assertItemsEquals(legal_captures(position), expected)
-end
-
-function test_position_with_lots_of_captures()
-	local position = {
-		turn = "white",
-		board = {
-			{"♚", nil, nil, "♔", "♝", nil, nil, "♖"},
-			{nil, "♖", "♜", "♕", "♞", "♕", "♘", nil},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{"♗", "♛", "♕", "♝", "♕", "♛", "♕", "♞"},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, "♕", "♝", "♕", "♛", "♕", "♘", "♗"},
-			{nil, nil, nil, nil, nil, nil, nil, nil},
-			{nil, nil, nil, "♜", "♕", "♛", nil, nil},
-		},
-		en_passant_target = {rank = 6, file = 4},
-	}
-	local expected = {
-		"♔xe1", "♔xe2", "♔xc2", "♖xh4", "♖xe1",
-		"♖xb4", "♖xc2", "♕xf4", "♕xb4", "♕xe1",
-		"♕xd4", "♕xe2", "♕xc2", "♕xh4", "♕xd4",
-		"♕xe1", "♕xf4", "♕xe2", "♘xh4", "♘xf4",
-		"♘xe1", "♗xc6", "♗xc2", "♕xe6", "♕xe2",
-		"♕xc6", "♕xc2", "♕xd4", "♕xb4", "♕xc6",
-		"♕xc2", "♕xe6", "♕xe2", "♕xf4", "♕xd4",
-		"♕xe6", "♕xe2", "♕xh4", "♕xf4", "♕xd8",
-		"♕xd4", "♕xb4", "♕xc6", "♕xf8", "♕xf4",
-		"♕xb4", "♕xd8", "♕xd4", "♕xe6", "♕xc6",
-		"♕xd8", "♕xh4", "♕xd4", "♕xf8", "♕xf4",
-		"♕xe6", "♘xf8", "♘xh4", "♘xf4", "♗xf8",
-		"♗xf4", "♕xc6", "♕xe6", "♕xf8", "♕xd8",
-	}
-	local captures = legal_captures(position)
-	luaunit.assertItemsEquals(captures, expected)
-end
-
-os.exit(luaunit.LuaUnit.run())

README.md

@@ -1,39 +1,13 @@
 # Lua Exercises
 
 This repo contains some Lua exercises along with automated tests for
-solutions.  Each file contains a description of the problem and an
+their solutions.  Each file contains a description of the problem and
-area for a solution as well as the tests.
+an area for your solution as well as the tests.  Feel free to define
-
+as many functions and constants as you need in the solution area, but
-## Set Up
+do not modify the tests.
-
-To get started, create a fork of this repo on your own account (with
-the "Fork" button in the top-left of the Gitea page"), then clone it,
-passing the `--recursive` flag.  If you already cloned it without
-passing `--recursive`, you can run `git submodule update --init` to
-fix it.
-
-```sh
-git clone --recursive git@git.wip.sh:<your-username>/lua-exercises.git
-```
-
-## Doing the Exercises
-
-It's recommended that you roughly stick to the defined order of the
-exercises, but feel free to deviate if you wish.  Some of the
-exercises are relatively easy, whereas some of them (especially the
-last few) are quite challenging; do not be disheartened if solving a
-particular exercise takes you a long time, and feel free to ask for
-help in the Discord server if you feel you are stuck.
-
-You can define as many functions and constants as you need in the
-solution area.  You might find it useful to temporarily comment out
-some of the tests to work through the cases one by one (especially on
-the more complex exercises), but do not modify the test code other
-than this, and make sure all the cases are un-commented again before
-considering the exercise solved.
 
 To run the tests and check your solution for a given exercise, simply
 run `lua <the-file>`.  For example, if you were working on the
-anagrams exercise, you would run `lua 08_anagrams.lua`.  For each
+anagrams exercise, you would run `lua xxx_anagrams.lua`.  For each
 exercise, the tests should run in well under a tenth of a second; if
 it takes longer than this you should try to speed up your solution.

greatest_common_divisor.lua

@@ -1,8 +1,6 @@
--- The greatest common divisor (GCD) of two numbers is, as the name
+-- The greatest common divisor (GCD) of two numbers X and Y is, as the
--- suggests, the largest number which evenly divides both.  Implement
+-- name suggests, the largest number which evenly divides both X and
--- the function below to calculate this.  It's recommended that you
+-- Y.  Implement the function below to calculate this.
--- use Euclid's algorithm but feel free to use another approach if you
--- want.
 --
 -- Solution --------------------------------------------------------------------
 function greatest_common_divisor(x, y)