feat: solve day 9 puzzle 1

src/day09/puzzle1.lua

@@ -0,0 +1,30 @@
+local utils = require "utils"
+local puzzle1 = {}
+
+function puzzle1.area(tile1, tile2)
+    local dx = math.abs(tile2.x - tile1.x) + 1
+    local dy = math.abs(tile2.y - tile1.y) + 1
+    return dx * dy
+end
+
+function puzzle1.solve(input)
+    local lines = utils.splitLines(input)
+    local tiles = {}
+
+    for _, line in ipairs(lines) do
+        local x, y = line:match("(%d+),(%d+)")
+        table.insert(tiles, {x=tonumber(x), y=tonumber(y)})
+    end
+
+    local maxArea = 0
+    for i, tile1 in ipairs(tiles) do
+        for j=i+1, #tiles do
+            local tile2 = tiles[j]
+            local area = puzzle1.area(tile1, tile2)
+            maxArea = math.max(maxArea, area)
+        end
+    end
+    return maxArea
+end
+
+return puzzle1