2021 - Day 25

2021/25/go.mod

@@ -0,0 +1,9 @@
+module AoC/2021/25
+
+require AoC/2021/common v0.0.0
+
+require github.com/joho/godotenv v1.4.0 // indirect
+
+replace AoC/2021/common v0.0.0 => ../common
+
+go 1.17

2021/25/go.sum

@@ -0,0 +1,2 @@
+github.com/joho/godotenv v1.4.0 h1:3l4+N6zfMWnkbPEXKng2o2/MR5mSwTrBih4ZEkkz1lg=
+github.com/joho/godotenv v1.4.0/go.mod h1:f4LDr5Voq0i2e/R5DDNOoa2zzDfwtkZa6DnEwAbqwq4=

2021/25/main.go

@@ -0,0 +1,165 @@
+package main
+
+import (
+	aoc "AoC/2021/common"
+	"bufio"
+	"fmt"
+)
+
+type Cucumber int
+
+const (
+	Empty Cucumber = iota
+	East
+	South
+)
+
+func (c Cucumber) String() string {
+	switch c {
+	case Empty:
+		return "."
+	case East:
+		return ">"
+	case South:
+		return "v"
+	default:
+		return fmt.Sprintf("%d", c)
+	}
+}
+
+type Grid [][]Cucumber
+
+func (g Grid) Print() {
+	for _, row := range g {
+		for _, c := range row {
+			fmt.Print(c)
+		}
+		fmt.Print("\n")
+	}
+}
+
+func (g Grid) stepEast() (Grid, int) {
+	counter := 0
+	ng := make(Grid, len(g))
+	for i := range g {
+		ng[i] = make([]Cucumber, len(g[i]))
+		for j := range g[i] {
+			ng[i][j] = g[i][j]
+		}
+	}
+
+	for i := range g {
+		if g[i][len(g[i])-1] == East && g[i][0] == Empty {
+			ng[i][0] = East
+			ng[i][len(g[i])-1] = Empty
+			counter++
+		}
+
+		for j := len(g[i]) - 2; j >= 0; j-- {
+			if g[i][j] == East && g[i][j+1] == Empty {
+				ng[i][j+1] = East
+				ng[i][j] = Empty
+				counter++
+			}
+		}
+	}
+
+	return ng, counter
+}
+
+func (g Grid) stepSouth() (Grid, int) {
+	counter := 0
+	ng := make(Grid, len(g))
+	for i := range g {
+		ng[i] = make([]Cucumber, len(g[i]))
+		for j := range g[i] {
+			ng[i][j] = g[i][j]
+		}
+	}
+
+	for j := range g[0] {
+		if g[len(g)-1][j] == South && g[0][j] == Empty {
+			ng[0][j] = South
+			ng[len(g)-1][j] = Empty
+			counter++
+		}
+	}
+
+	for i := len(g)-2; i >= 0; i-- {
+		for j := range g[i] {
+			if g[i][j] == South && g[i+1][j] == Empty {
+				ng[i+1][j] = South
+				ng[i][j] = Empty
+				counter++
+			}
+		}
+	}
+
+	return ng, counter
+}
+
+func (g Grid) Step() (Grid, int) {
+	var a, b int
+	g, a = g.stepEast()
+	g, b = g.stepSouth()
+	return g, a+b
+}
+
+func main() {
+	challenge := aoc.New(2021, 25)
+
+	challenge.Test(`v...>>.vv>
+.vv>>.vv..
+>>.>v>...v
+>>v>>.>.v.
+v>v.vv.v..
+>.>>..v...
+.vv..>.>v.
+v.v..>>v.v
+....v..v.>`, []int{58, -1})
+
+	challenge.Solution(1, func(input *bufio.Scanner) int {
+		var grid Grid
+
+		for input.Scan() {
+			line := input.Text()
+
+			row := make([]Cucumber, len(line))
+			for i, c := range line {
+				switch c {
+				case '>':
+					row[i] = East
+				case 'v':
+					row[i] = South
+				default:
+					row[i] = Empty
+				}
+			}
+
+			grid = append(grid, row)
+		}
+
+		// grid.Print()
+
+		noMovementAfter := 1
+		for ; true; noMovementAfter++ {
+			var moved int
+			grid, moved = grid.Step()
+
+// 			fmt.Println("\nSTEP", noMovementAfter+1)
+// 			grid.Print()
+
+			if moved == 0 {
+				break
+			}
+		}
+
+		grid.Print()
+
+		return noMovementAfter
+	})
+
+	challenge.Solution(2, func(input *bufio.Scanner) int {
+		return 0
+	})
+}