Solve p19 in lua

README.rst

@@ -103,7 +103,7 @@ Olivia's Project Euler Solutions
    |            | Browser [#]_               |        | |CodeQL| |br|     |
    |            |                            |        | |ESLint|          |
    +------------+----------------------------+--------+-------------------+
-   | Lua        | PUC-Rio Lua 5+ [#]_        | 22     | |Luai| |br|       |
+   | Lua        | PUC-Rio Lua 5+ [#]_        | 23     | |Luai| |br|       |
    |            |                            |        | |Lu-Cov| |br|     |
    |            |                            |        | |LuaCheck|        |
    +------------+----------------------------+--------+-------------------+

docs/index.rst

@@ -114,7 +114,7 @@ Problems Solved
   +-----------+-----------+------------+------------+------------+------------+------------+------------+------------+------------+
   |:prob:`018`|           |            |            |            |            |:js-d:`0018`|            |:py-d:`0018`|:rs-d:`0018`|
   +-----------+-----------+------------+------------+------------+------------+------------+------------+------------+------------+
-  |:prob:`019`|:c-d:`0019`|:cp-d:`0019`|:cs-d:`0019`|            |:ja-d:`0019`|:js-d:`0019`|            |:py-d:`0019`|:rs-d:`0019`|
+  |:prob:`019`|:c-d:`0019`|:cp-d:`0019`|:cs-d:`0019`|            |:ja-d:`0019`|:js-d:`0019`|:lu-d:`0019`|:py-d:`0019`|:rs-d:`0019`|
   +-----------+-----------+------------+------------+------------+------------+------------+------------+------------+------------+
   |:prob:`020`|:c-d:`0020`|:cp-d:`0020`|:cs-d:`0020`|:fr-d:`0020`|:ja-d:`0020`|:js-d:`0020`|:lu-d:`0020`|:py-d:`0020`|:rs-d:`0020`|
   +-----------+-----------+------------+------------+------------+------------+------------+------------+------------+------------+

docs/src/fortran/p0019.rst

@@ -0,0 +1,14 @@
+Fortran Implementation of Problem 19
+====================================
+
+View source code :source:`fortran/src/p0019.f90`
+
+.. f:module:: Problem0019
+
+.. f:function:: integer Problem0019/p0019()
+
+.. literalinclude:: ../../../fortran/src/p0019.f90
+   :language: Fortran
+   :linenos:
+
+.. tags:: calendar, combinatorics

lua/README.rst

@@ -75,6 +75,7 @@ Problems Solved
 -  ☒ `15 <./src/p0015.lua>`__
 -  ☒ `16 <./src/p0016.lua>`__
 -  ☒ `17 <./src/p0017.lua>`__
+-  ☒ `19 <./src/p0019.lua>`__
 -  ☒ `20 <./src/p0020.lua>`__
 -  ☒ `22 <./src/p0022.lua>`__
 -  ☒ `28 <./src/p0028.lua>`__

lua/src/p0019.lua

@@ -0,0 +1,39 @@
+-- Project Euler Problem 19
+--
+-- This one ended up being very easy thanks to the time library
+--
+-- Problem:
+--
+-- You are given the following information, but you may prefer to do some research
+-- for yourself.
+--
+--     1 Jan 1900 was a Monday.
+--     Thirty days has September,
+--     April, June and November.
+--     All the rest have thirty-one,
+--     Saving February alone,
+--     Which has twenty-eight, rain or shine.
+--     And on leap years, twenty-nine.
+--     A leap year occurs on any year evenly divisible by 4, but not on a century
+--     unless it is divisible by 400.
+--
+-- How many Sundays fell on the first of the month during the twentieth century
+-- (1 Jan 1901 to 31 Dec 2000)?
+
+local function is_sunday(year, month, day)
+    return os.date("*t", os.time({year=year, month=month, day=day})).wday == 1
+end
+
+return {
+    solution = function()
+        local answer = 0
+        for year = 1901, 2000 do
+            for month = 1, 12 do
+                if is_sunday(year, month, 1) then
+                    answer = answer + 1
+                end
+            end
+        end
+        return answer
+    end
+}

lua/test.lua

@@ -84,6 +84,8 @@ for i = 13, 17 do
 end
 
 local more_problems = {
+    ["p0019.lua"] = {get_answer(19), false},
+    ["p0020.lua"] = {get_answer(20), false},
     ["p0022.lua"] = {get_answer(22), false},
     ["p0028.lua"] = {get_answer(28), false},
     ["p0034.lua"] = {get_answer(34), false},