2020 day 2

2020/2/day2.lua

@@ -0,0 +1,35 @@
+#!/usr/bin/env lua
+
+local data = {}
+
+for line in io.lines() do
+    local password_start, n1, n2, char = select(2, line:find('^(%d+)-(%d+) (%l): '))
+    table.insert(data, {tonumber(n1), tonumber(n2), char, line:sub(password_start + 1)})
+end
+
+local function part1()
+    local count = 0
+    for _, line in ipairs(data) do
+        local min, max, char, password = table.unpack(line)
+        local char_count = select(2, password:gsub(char, ''))
+        if min <= char_count and char_count <= max then
+            count = count + 1
+        end
+    end
+    return count
+end
+
+local function part2()
+    local count = 0
+    for _, line in ipairs(data) do
+        local pos1, pos2, char, password = table.unpack(line)
+        local has1, has2 = password:sub(pos1, pos1) == char, password:sub(pos2, pos2) == char
+        if (has1 or has2) and not (has1 and has2) then
+            count = count + 1
+        end
+    end
+    return count
+end
+
+print(part1())
+print(part2())

README.md

@@ -7,7 +7,7 @@ My solutions to the Advent of Code puzzles.
 ```
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