day10 part 1 solution

puzzles/day10/main.go

@@ -0,0 +1,145 @@
+package main
+
+import (
+	"fmt"
+	"github.com/kylehoehns/aoc-2023-go/pkg/files"
+	"strings"
+)
+
+func main() {
+	fmt.Println("Part 1: ", part1("input.txt"))
+	fmt.Println("Part 2: ", part2("input.txt"))
+}
+
+func part1(name string) int {
+
+	lines := files.ReadLines(name)
+	grid := make([][]string, 0)
+	for _, line := range lines {
+		grid = append(grid, strings.Split(line, ""))
+	}
+	startRow, startCol := findStartingPosition(grid)
+
+	steps := 1
+
+	row, col := determineFirstStep(grid, startRow, startCol)
+
+	priorRow := startRow
+	priorCol := startCol
+	// from the 2nd position, move along the pipe and keep track of the number of steps we take until we get back to S
+	for !(col == startCol && row == startRow) {
+		steps++
+		nextRow := row
+		nextCol := col
+		if grid[row][col] == "|" {
+			if row > priorRow {
+				// if we are moving south, move down
+				nextRow++
+			} else {
+				// if we are moving north, move up
+				nextRow--
+			}
+		} else if grid[row][col] == "-" {
+			if col > priorCol {
+				// from the left, go right
+				nextCol++
+			} else {
+				// from the right, go left
+				nextCol--
+			}
+		} else if grid[row][col] == "L" {
+			// 90 degree connecting north and east
+			if priorRow < row {
+				// we're coming into this from the top, so go right
+				nextCol++
+			} else {
+				// we're coming into this from the right, so go up
+				nextRow--
+			}
+		} else if grid[row][col] == "J" {
+			// 90 degree connecting north and west
+			if priorCol < col {
+				// we're coming into this from the left, so go up and right
+				nextRow--
+			} else {
+				// we're coming into this from the top, so go down and left
+				nextCol--
+			}
+		} else if grid[row][col] == "F" {
+			// 90 degree connecting south and east
+			if priorRow > row {
+				// from the bottom, go right
+				nextCol++
+			} else {
+				// from the right, go down
+				nextRow++
+			}
+		} else if grid[row][col] == "7" {
+			// 90 degree connecting south and west
+			if priorRow > row {
+				// from the bottom, go up and left
+				nextCol--
+			} else {
+				// from the left, go down and right
+				nextRow++
+			}
+		}
+
+		priorRow = row
+		priorCol = col
+		row = nextRow
+		col = nextCol
+	}
+
+	return steps / 2
+}
+
+func determineFirstStep(grid [][]string, startRow int, startCol int) (int, int) {
+	row := startRow
+	col := startCol
+	// look at cells around the starting position and see if any of them connect in a way that we can follow them
+	if grid[startRow-1][startCol] == "|" {
+		// move north
+		row--
+	} else if grid[startRow+1][startCol] == "|" {
+		// move south
+		row++
+	} else if grid[startRow][startCol-1] == "-" {
+		// move west
+		col--
+	} else if grid[startRow][startCol+1] == "-" {
+		// move east
+		col++
+	} else if grid[startRow+1][startCol] == "L" {
+		// 90 degree connecting north and east
+		row++
+	} else if grid[startRow+1][startCol] == "J" {
+		// 90 degree connecting north and west
+		row++
+	} else if grid[startRow-1][startCol] == "F" {
+		// 90 degree connecting south and east
+		row--
+	} else if grid[startRow-1][startCol] == "7" {
+		// 90 degree connecting south and west
+		row--
+	}
+	return row, col
+}
+
+func findStartingPosition(grid [][]string) (int, int) {
+	// find the location of the first "S"
+	var startRow, startCol int
+	for row, line := range grid {
+		for col, char := range line {
+			if char == "S" {
+				startRow = row
+				startCol = col
+			}
+		}
+	}
+	return startRow, startCol
+}
+
+func part2(name string) int {
+	return 0
+}

puzzles/day10/main_test.go

@@ -0,0 +1,33 @@
+package main
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestPart1(t *testing.T) {
+
+	t.Run("Part 1 Simple", func(t *testing.T) {
+		expected := 4
+		actual := part1("test-input.txt")
+		assert.Equal(t, expected, actual)
+	})
+
+	t.Run("Part 1 Harder", func(t *testing.T) {
+		expected := 8
+		actual := part1("test-input-2.txt")
+		assert.Equal(t, expected, actual)
+	})
+
+}
+
+func TestPart2(t *testing.T) {
+
+	t.Run("Part 2", func(t *testing.T) {
+		expected := 0
+		actual := part2("test-input.txt")
+		assert.Equal(t, expected, actual)
+	})
+
+}

puzzles/day10/test-input-2.txt

@@ -0,0 +1,5 @@
+7-F7-
+.FJ|7
+SJLL7
+|F--J
+LJ.LJ

puzzles/day10/test-input.txt

@@ -0,0 +1,5 @@
+-L|F7
+7S-7|
+L|7||
+-L-J|
+L|-JF