From 44b8be5a9e34c0227556a70041dea28d208a338e Mon Sep 17 00:00:00 2001
From: Stefan Harmuth <stefan.harmuth@docomodigital.com>
Date: Sun, 24 Oct 2021 20:59:45 +0200
Subject: [PATCH] day18

---
 day18/day.go   | 41 +++++++++++++++++++++++++++++++++++++++++
 inputs/18      |  1 +
 inputs/18_test |  1 +
 main.go        |  3 ++-
 4 files changed, 45 insertions(+), 1 deletion(-)
 create mode 100644 day18/day.go
 create mode 100644 inputs/18
 create mode 100644 inputs/18_test

diff --git a/day18/day.go b/day18/day.go
new file mode 100644
index 0000000..204e33a
--- /dev/null
+++ b/day18/day.go
@@ -0,0 +1,41 @@
+package day18
+
+import (
+	"tools"
+)
+
+func getGridFromInput(inp string) tools.GridToggle {
+	grid := tools.NewGridToggle()
+	for i, c := range inp {
+		grid.Set(i, 0, c == '^')
+	}
+	return grid
+}
+
+func calcTraps(grid tools.GridToggle, cols, rows int) tools.GridToggle {
+	for row := 1; row < rows; row++ {
+		for x := 0; x < cols; x++ {
+			grid.Set(x, row,
+				(grid.State(x-1, row-1) && grid.State(x, row-1) && !grid.State(x+1, row-1)) ||
+					(!grid.State(x-1, row-1) && grid.State(x, row-1) && grid.State(x+1, row-1)) ||
+					(grid.State(x-1, row-1) && !grid.State(x, row-1) && !grid.State(x+1, row-1)) ||
+					(!grid.State(x-1, row-1) && !grid.State(x, row-1) && grid.State(x+1, row-1)))
+		}
+	}
+
+	return grid
+}
+
+func Part1(puzzle tools.AoCPuzzle) interface{} {
+	inp := puzzle.GetInputString()
+	width := len(inp)
+	field := calcTraps(getGridFromInput(inp), width, 40)
+	return (field.MaxX+1)*(field.MaxY+1) - field.GetOnCount()
+}
+
+func Part2(puzzle tools.AoCPuzzle) interface{} {
+	inp := puzzle.GetInputString()
+	width := len(inp)
+	field := calcTraps(getGridFromInput(inp), width, 400000)
+	return (field.MaxX+1)*(field.MaxY+1) - field.GetOnCount()
+}
diff --git a/inputs/18 b/inputs/18
new file mode 100644
index 0000000..a86a628
--- /dev/null
+++ b/inputs/18
@@ -0,0 +1 @@
+^.^^^.^..^....^^....^^^^.^^.^...^^.^.^^.^^.^^..^.^...^.^..^.^^.^..^.....^^^.^.^^^..^^...^^^...^...^.
\ No newline at end of file
diff --git a/inputs/18_test b/inputs/18_test
new file mode 100644
index 0000000..235ef50
--- /dev/null
+++ b/inputs/18_test
@@ -0,0 +1 @@
+.^^.^.^^^^
\ No newline at end of file
diff --git a/main.go b/main.go
index 1101620..f804b3f 100644
--- a/main.go
+++ b/main.go
@@ -17,6 +17,7 @@ import (
 	"aoc2016/day15"
 	"aoc2016/day16"
 	"aoc2016/day17"
+	"aoc2016/day18"
 	"flag"
 	"fmt"
 	"os"
@@ -51,7 +52,7 @@ func initDayFunctions() {
 		15: {1: day15.Part1, 2: day15.Part2},
 		16: {1: day16.Part1, 2: day16.Part2},
 		17: {1: day17.Part1, 2: day17.Part2},
-		//		18: {1: day18.Part1, 2: day18.Part2},
+		18: {1: day18.Part1, 2: day18.Part2},
 		//		19: {1: day19.Part1, 2: day19.Part2},
 		//		20: {1: day20.Part1, 2: day20.Part2},
 		//		21: {1: day21.Part1, 2: day21.Part2},