Day 5: Add Lua solution

05/solution_1.lua

@@ -0,0 +1,33 @@
+#!/usr/bin/env lua
+
+map = {}
+
+for line in io.lines("input.txt")  do
+    x0, y0, x1, y1 = string.match(line, "(%d+),(%d+) .+ (%d+),(%d+)")
+    x0 = tonumber(x0) x1 = tonumber(x1) y0 = tonumber(y0) y1 = tonumber(y1)
+
+    if x0 == x1 then
+        map[x0] = map[x0] or {}
+        if y0 > y1 then step = -1 else step = 1 end
+        for y = y0, y1, step do
+            map[x0][y] = (map[x0][y] or 0) + 1
+        end
+    elseif y0 == y1 then
+        if x0 > x1 then step = -1 else step = 1 end
+        for x = x0, x1, step do
+            map[x] = map[x] or {}
+            map[x][y0] = (map[x][y0] or 0) + 1
+        end
+    end
+end
+
+intersections = 0
+for _, col in pairs(map) do
+    for _, f in pairs(col) do
+        if f > 1 then
+            intersections = intersections + 1
+        end
+    end
+end
+
+print("Answer:", intersections)

05/solution_2.lua

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+#!/usr/bin/env lua
+
+map = {}
+
+for line in io.lines("input.txt")  do
+    x0, y0, x1, y1 = string.match(line, "(%d+),(%d+) .+ (%d+),(%d+)")
+    x0 = tonumber(x0) x1 = tonumber(x1) y0 = tonumber(y0) y1 = tonumber(y1)
+
+    if y0 > y1 then ystep = -1 else ystep = 1 end
+    if x0 > x1 then xstep = -1 else xstep = 1 end
+
+    if x0 == x1 then
+        map[x0] = map[x0] or {}
+        for y = y0, y1, ystep do
+            map[x0][y] = (map[x0][y] or 0) + 1
+        end
+    elseif y0 == y1 then
+        for x = x0, x1, xstep do
+            map[x] = map[x] or {}
+            map[x][y0] = (map[x][y0] or 0) + 1
+        end
+    else
+        x = x0 y = y0
+        while x ~= x1 and y ~= y1 do
+            map[x] = map[x] or {}
+            map[x][y] = (map[x][y] or 0) + 1
+            x = x + xstep
+            y = y + ystep
+        end
+        map[x] = map[x] or {}
+        map[x][y] = (map[x][y] or 0) + 1
+    end
+end
+
+intersections = 0
+for _, col in pairs(map) do
+    for _, f in pairs(col) do
+        if f > 1 then
+            intersections = intersections + 1
+        end
+    end
+end
+
+print("Answer:", intersections)