aoc24/day4/main.go

package main

import (
	"fmt"

	"git.mstar.dev/mstar/aoc24/util"
	"git.mstar.dev/mstar/goutils/sliceutils"
)

type Coord struct {
	X, Y int
	C    rune
}

// Ugly but works
var allOffsets1 = [][]Coord{
	{newCoord(0, 0, 'X'), newCoord(0, 1, 'M'), newCoord(0, 2, 'A'), newCoord(0, 3, 'S')},
	{newCoord(0, 0, 'X'), newCoord(0, -1, 'M'), newCoord(0, -2, 'A'), newCoord(0, -3, 'S')},
	{newCoord(0, 0, 'X'), newCoord(1, 0, 'M'), newCoord(2, 0, 'A'), newCoord(3, 0, 'S')},
	{newCoord(0, 0, 'X'), newCoord(-1, 0, 'M'), newCoord(-2, 0, 'A'), newCoord(-3, 0, 'S')},
	{newCoord(0, 0, 'X'), newCoord(1, 1, 'M'), newCoord(2, 2, 'A'), newCoord(3, 3, 'S')},
	{newCoord(0, 0, 'X'), newCoord(-1, -1, 'M'), newCoord(-2, -2, 'A'), newCoord(-3, -3, 'S')},
	{newCoord(0, 0, 'X'), newCoord(1, -1, 'M'), newCoord(2, -2, 'A'), newCoord(3, -3, 'S')},
	{newCoord(0, 0, 'X'), newCoord(-1, 1, 'M'), newCoord(-2, 2, 'A'), newCoord(-3, 3, 'S')},
}

var allOffsets2 = [][]Coord{
	{
		newCoord(0, 0, 'A'),
		newCoord(-1, -1, 'M'),
		newCoord(-1, 1, 'M'),
		newCoord(1, 1, 'S'),
		newCoord(1, -1, 'S'),
	},
	{
		newCoord(0, 0, 'A'),
		newCoord(-1, -1, 'S'),
		newCoord(-1, 1, 'M'),
		newCoord(1, 1, 'M'),
		newCoord(1, -1, 'S'),
	},
	{
		newCoord(0, 0, 'A'),
		newCoord(-1, -1, 'S'),
		newCoord(-1, 1, 'S'),
		newCoord(1, 1, 'M'),
		newCoord(1, -1, 'M'),
	},
	{
		newCoord(0, 0, 'A'),
		newCoord(-1, -1, 'M'),
		newCoord(-1, 1, 'S'),
		newCoord(1, 1, 'S'),
		newCoord(1, -1, 'M'),
	},
}

func newCoord(x, y int, C rune) Coord { return Coord{x, y, C} }

func linesToGrid(lines []string) [][]rune {
	return sliceutils.Map(lines, func(t string) []rune { return []rune(t) })
}

func safeAccess(grid [][]rune, x, y int) (bool, rune) {
	if x < 0 {
		return false, ' '
	}
	if y < 0 {
		return false, ' '
	}
	if x >= len(grid[0]) {
		return false, ' '
	}
	if y >= len(grid) {
		return false, ' '
	}
	return true, grid[y][x]
}

func checkGridWithOffsets(x, y int, grid [][]rune, allOffsets [][]Coord) int {
	acc := 0
outer:
	for _, offsets := range allOffsets {
		for _, offset := range offsets {
			ok, r := safeAccess(grid, x+offset.X, y+offset.Y)
			if !ok {
				continue outer
			}
			if offset.C != r {
				continue outer
			}
		}
		acc++
	}
	if acc != 0 {
		// fmt.Printf("Found %d at %d:%d\n", acc, x, y)
	}
	return acc
}

func main() {
	grid := linesToGrid(util.FileContentToNonEmptyLines(util.LoadFileFromArgs()))
	counter := 0
	for iy := range grid {
		for ix := range grid[iy] {
			counter += checkGridWithOffsets(ix, iy, grid, allOffsets1)
		}
	}
	fmt.Printf("Task 1: %d\n", counter)
	counter = 0
	for iy := range grid {
		for ix := range grid[iy] {
			counter += checkGridWithOffsets(ix, iy, grid, allOffsets2)
		}
	}
	fmt.Printf("Task 2: %d\n", counter)
}