2021-advent-15.go

package main

import (
	"fmt"
	"io/ioutil"
	"log"
	"math"
	"strconv"
	"strings"
)

func prettyPrint(val [][]int) {
	for y := range val {
		for x := range val[y] {
			fmt.Print(val[y][x])
		}
		fmt.Println()
	}
}

func readInput(input string) [][]int {
	bytes, err := ioutil.ReadFile(input)
	if err != nil {
		log.Fatal(err)
	}
	lines := strings.Split(string(bytes), "\n")
	cave := make([][]int, 0)
	for _, line := range lines {
		row := make([]int, 0, 16)
		for _, rune := range line {
			height, err := strconv.Atoi(string(rune))
			if err != nil {
				log.Fatal(err)
			}
			row = append(row, height)
		}
		cave = append(cave, row)
	}
	return cave
}

type coord struct {
	x, y int
}

func shortestPath(data [][]int) int {
	weights := make(map[coord]int)
	queue := make([]coord, 0, 512)
	for y := range data {
		for x := range data[y] {
			weights[coord{x, y}] = math.MaxInt
		}
	}
	weights[coord{0, 0}] = 0

	queue = append(queue, coord{0, 0})
	for len(queue) > 0 {
		pop := queue[0]
		queue = queue[1:]
		for _, neighbourCoord := range []coord{
			{pop.x + 1, pop.y},
			{pop.x, pop.y + 1},
			{pop.x - 1, pop.y},
			{pop.x, pop.y - 1},
		} {
			_, ok := weights[neighbourCoord]
			if !ok {
				continue
			}
			if newCost := weights[pop] + data[neighbourCoord.y][neighbourCoord.x]; newCost < weights[neighbourCoord] {
				weights[neighbourCoord] = newCost
				queue = append(queue, neighbourCoord)
			}
		}
	}
	totalCost := weights[coord{len(data[0]) - 1, len(data) - 1}]
	return totalCost
}

func task1(input string) {
	data := readInput(input)
	cost := shortestPath(data)
	fmt.Printf("Day15 task1 %s - %d\n", input, cost)

}
func task2(input string) {
	data := readInput(input)

	small_y := len(data)
	small_x := len(data[0])

	globalMap := make([][]int, small_y*5)

	for i := 0; i < small_y*5; i++ {
		globalMap[i] = make([]int, 5*small_x)
	}

	for y, row := range data {
		for x, item := range row {
			for i := 0; i < 5; i++ {
				for j := 0; j < 5; j++ {
					newVal := (item + i + j)
					if newVal > 9 {
						newVal = newVal % 9
					}
					globalMap[y+(i*small_y)][x+(j*small_x)] = newVal
				}
			}
		}
	}
	// prettyPrint(globalMap)
	cost := shortestPath(globalMap)
	fmt.Printf("Day15 task1 %s - %d\n", input, cost)
}

func main() {
	task1("example.txt")
	task1("input.txt")
	task2("example.txt")
	task2("input.txt")
}