2024-day14, using new go range over ints

2023/day14/main.go

@@ -0,0 +1,185 @@
+package main
+
+import (
+	_ "embed"
+	"flag"
+	"fmt"
+	"strings"
+
+	"github.com/alexchao26/advent-of-code-go/util"
+)
+
+//go:embed input.txt
+var input string
+
+func init() {
+	// do this in init (not main) so test file has same input
+	input = strings.TrimRight(input, "\n")
+	if len(input) == 0 {
+		panic("empty input.txt file")
+	}
+}
+
+func main() {
+	var part int
+	flag.IntVar(&part, "part", 1, "part 1 or 2")
+	flag.Parse()
+	fmt.Println("Running part", part)
+
+	if part == 1 {
+		ans := part1(input)
+		util.CopyToClipboard(fmt.Sprintf("%v", ans))
+		fmt.Println("Output:", ans)
+	} else {
+		ans := part2(input)
+		util.CopyToClipboard(fmt.Sprintf("%v", ans))
+		fmt.Println("Output:", ans)
+	}
+}
+
+func part1(input string) int {
+	grid := parseInput(input)
+
+	// tilt north, all O's roll to the top or to the next #
+	tiltNorth(grid)
+
+	// then calculate total load (total rows) - (row index) per rock
+	ans := 0
+	for r, row := range grid {
+		for _, val := range row {
+			if val == "O" {
+				ans += len(grid) - r
+			}
+		}
+	}
+
+	return ans
+}
+
+func part2(input string) int {
+	grid := parseInput(input)
+
+	seenStates := map[string]int{}
+
+	cycles := 1000000000
+	for c := 0; c < cycles; c++ {
+		key := stringifyStringGrid(grid)
+		if lastIndex, ok := seenStates[key]; ok {
+			cyclePeriod := c - lastIndex
+			for c+cyclePeriod < cycles {
+				c += cyclePeriod
+			}
+		}
+		seenStates[key] = c
+
+		// 1 cycle = tilt N, W, S, E
+		tiltNorth(grid)
+		tiltWest(grid)
+		tiltSouth(grid)
+		tiltEast(grid)
+	}
+
+	ans := 0
+	for r, row := range grid {
+		for _, val := range row {
+			if val == "O" {
+				ans += len(grid) - r
+			}
+		}
+	}
+
+	// 99841 too low
+	return ans
+}
+
+func tiltNorth(grid [][]string) {
+	for r, row := range grid {
+		for c, val := range row {
+			if val == "O" {
+				for nextRow := r - 1; nextRow >= 0; nextRow-- {
+					// can only fall north if nextRow is an empty space
+					if grid[nextRow][c] == "." {
+						grid[nextRow][c] = "O"
+						grid[nextRow+1][c] = "."
+					} else {
+						break
+					}
+				}
+			}
+		}
+	}
+}
+
+func tiltSouth(grid [][]string) {
+	for r := len(grid) - 1; r >= 0; r-- {
+		for c := range len(grid[0]) {
+			val := grid[r][c]
+			if val == "O" {
+				for nextRow := r + 1; nextRow < len(grid); nextRow++ {
+					// can only fall north if nextRow is an empty space
+					if grid[nextRow][c] == "." {
+						grid[nextRow][c] = "O"
+						grid[nextRow-1][c] = "."
+					} else {
+						break
+					}
+				}
+			}
+		}
+	}
+}
+
+func tiltEast(grid [][]string) {
+	for c := len(grid[0]) - 1; c >= 0; c-- {
+		for r := range grid {
+			val := grid[r][c]
+
+			if val == "O" {
+				for nextCol := c + 1; nextCol < len(grid[0]); nextCol++ {
+					// can only fall north if nextCol is an empty space
+					if grid[r][nextCol] == "." {
+						grid[r][nextCol] = "O"
+						grid[r][nextCol-1] = "."
+					} else {
+						break
+					}
+				}
+			}
+		}
+	}
+}
+
+func tiltWest(grid [][]string) {
+	for c := range len(grid[0]) {
+		for r := range grid {
+			val := grid[r][c]
+
+			if val == "O" {
+				for nextCol := c - 1; nextCol >= 0; nextCol-- {
+					// can only fall north if nextCol is an empty space
+					if grid[r][nextCol] == "." {
+						grid[r][nextCol] = "O"
+						grid[r][nextCol+1] = "."
+					} else {
+						break
+					}
+				}
+			}
+		}
+	}
+}
+
+func stringifyStringGrid(grid [][]string) string {
+	ans := ""
+	for _, row := range grid {
+		ans += strings.Join(row, "")
+	}
+	return ans
+}
+
+func parseInput(input string) (ans [][]string) {
+	for _, line := range strings.Split(input, "\n") {
+		ans = append(ans, strings.Split(line, ""))
+	}
+	return ans
+}

2023/day14/main_test.go

@@ -0,0 +1,68 @@
+package main
+
+import (
+	"testing"
+)
+
+var example = `O....#....
+O.OO#....#
+.....##...
+OO.#O....O
+.O.....O#.
+O.#..O.#.#
+..O..#O..O
+.......O..
+#....###..
+#OO..#....`
+
+func Test_part1(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		want  int
+	}{
+		{
+			name:  "example",
+			input: example,
+			want:  136,
+		},
+		{
+			name:  "actual",
+			input: input,
+			want:  108840,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := part1(tt.input); got != tt.want {
+				t.Errorf("part1() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func Test_part2(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		want  int
+	}{
+		{
+			name:  "example",
+			input: example,
+			want:  64,
+		},
+		{
+			name:  "actual",
+			input: input,
+			want:  103445,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := part2(tt.input); got != tt.want {
+				t.Errorf("part2() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}