From b2ff2ac24c26a62f4e749226b1d3c99ed4771e8c Mon Sep 17 00:00:00 2001
From: David Ashby <delta.mu.alpha@gmail.com>
Date: Mon, 27 Dec 2021 12:30:38 -0700
Subject: [PATCH] day 25 done

---
 25/main.go | 112 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 112 insertions(+)
 create mode 100644 25/main.go

diff --git a/25/main.go b/25/main.go
new file mode 100644
index 0000000..6c1bb79
--- /dev/null
+++ b/25/main.go
@@ -0,0 +1,112 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"time"
+)
+
+func main() {
+	start := time.Now()
+	partOne()
+	duration := time.Since(start)
+	fmt.Printf("p1: %s\n", duration)
+}
+
+func makeScanner(test bool) *bufio.Scanner {
+	var f *os.File
+	if test {
+		f, _ = os.Open("inputs/testinput")
+	} else {
+		f, _ = os.Open("inputs/input")
+	}
+	reader := bufio.NewReader(f)
+	return bufio.NewScanner(reader)
+}
+
+type coord struct {
+	x int
+	y int
+}
+
+type floor struct {
+	steps  int
+	width  int
+	height int
+	m      map[coord]rune
+}
+
+func (f *floor) Print() {
+	for y := 0; y < f.height; y++ {
+		for x := 0; x < f.width; x++ {
+			fmt.Printf("%s", string(f.m[coord{x: x, y: y}]))
+		}
+		fmt.Printf("\n")
+	}
+	fmt.Printf("\n")
+}
+
+func (f *floor) Step() bool {
+	f.steps++
+	movedThisStep := map[coord]struct{}{}
+	toMove := map[coord]coord{}
+	for y := 0; y < f.height; y++ {
+		for x := 0; x < f.width; x++ {
+			current := coord{x: x, y: y}
+			x += 1
+			if x >= f.width {
+				x = 0
+			}
+			next := coord{x: x, y: y}
+			if _, ok := movedThisStep[current]; !ok && f.m[current] == '>' && f.m[next] == '.' {
+				toMove[current] = next
+			}
+		}
+	}
+	for current, next := range toMove {
+		f.m[next] = f.m[current]
+		f.m[current] = '.'
+		movedThisStep[next] = struct{}{}
+	}
+	toMove = map[coord]coord{}
+	for y := 0; y < f.height; y++ {
+		for x := 0; x < f.width; x++ {
+			current := coord{x: x, y: y}
+			y += 1
+			if y >= f.height {
+				y = 0
+			}
+			next := coord{x: x, y: y}
+			if _, ok := movedThisStep[current]; !ok && f.m[current] == 'v' && f.m[next] == '.' {
+				toMove[current] = next
+			}
+		}
+	}
+	for current, next := range toMove {
+		f.m[next] = f.m[current]
+		f.m[current] = '.'
+		movedThisStep[next] = struct{}{}
+	}
+	return len(movedThisStep) > 0
+}
+
+func partOne() {
+	scanner := makeScanner(false)
+	f := &floor{
+		m: make(map[coord]rune),
+	}
+	y := 0
+	for scanner.Scan() {
+		line := scanner.Text()
+		f.width = len(line)
+		for x, v := range line {
+			f.m[coord{x: x, y: y}] = v
+		}
+		y++
+	}
+	f.height = y
+	for f.Step() {
+	}
+	fmt.Println(f.steps)
+}