[KnowIt - 2020] Day Two - Add Lua solution

KnowItJulekalender/2020/02/gifts.lua

@@ -0,0 +1,45 @@
+local min = 0
+local max = 5433000
+local total = 0
+
+local function isPrime(num)
+    if num <= 2 then
+        return false
+    end
+
+    if num % 2 == 0 then
+        return false
+    end
+
+    for i = 2, (num - 1) do
+        if num % i == 0 then
+            return false
+        end
+    end
+
+    return true
+end
+
+-- Finn nærmeste primtall som er lavere enn `max`
+local function findPrime(max)
+    for count = max, 3, -1 do
+        if isPrime(count) then
+            return count
+        end
+    end
+end
+
+local gifts = min
+while gifts < max do
+    local hasSeven = tostring(gifts):match('7')
+
+    if hasSeven ~= nil then
+        gifts = gifts + findPrime(gifts)
+    else
+        total = total + 1
+    end
+
+    gifts = gifts + 1
+end
+
+print(total)