From fa33a7bdf75a9171ad09f70d71feefee69c7d3c2 Mon Sep 17 00:00:00 2001
From: Camden Dixie O'Brien <cdo@wip.sh>
Date: Thu, 14 Dec 2023 13:47:28 +0000
Subject: [PATCH] Create dependencies exercise

---
 19_dependencies.lua | 105 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 105 insertions(+)
 create mode 100644 19_dependencies.lua

diff --git a/19_dependencies.lua b/19_dependencies.lua
new file mode 100644
index 0000000..ce72051
--- /dev/null
+++ b/19_dependencies.lua
@@ -0,0 +1,105 @@
+-- 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())