AdventOfCode2021/15/main.go

package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
	"time"
)

func mustAtoi(line string) int {
	i, _ := strconv.Atoi(line)
	return i
}

func main() {
	start := time.Now()
	partOne()
	duration := time.Since(start)
	partTwo()
	duration2 := time.Since(start)
	fmt.Printf("p1: %s, p2: %s\n", duration, duration2-duration)
}

func makeScanner(test bool) *bufio.Scanner {
	var f *os.File
	if test {
		f, _ = os.Open("inputs/testinput")
	} else {
		f, _ = os.Open("inputs/input")
	}
	reader := bufio.NewReader(f)
	return bufio.NewScanner(reader)
}

type room struct {
	row      int
	col      int
	distance int
	cost     int
}

func partOne() {
	scanner := makeScanner(false)

	grid := [100][100]room{}
	col := 0
	for scanner.Scan() {
		line := scanner.Text()
		for row, v := range line {
			r := room{
				distance: 1000,
				cost:     mustAtoi(string(v)),
			}
			grid[row][col] = r
		}
		col++
	}
	grid[0][0].distance = 0

	for row := 0; row < 100; row++ {
		for col := 0; col < 100; col++ {
			if col+1 < 100 {
				d := grid[row][col+1].distance
				// if the cost of the space is less than the current known distance, this is the best route there
				if d > grid[row][col+1].cost+grid[row][col].distance {
					grid[row][col+1].distance = grid[row][col].distance + grid[row][col+1].cost
				}
			}
			if row+1 < 100 {
				d := grid[row+1][col].distance
				// if the cost of the space is less than the current known distance, this is the best route there
				if d > grid[row+1][col].cost+grid[row][col].distance {
					grid[row+1][col].distance = grid[row][col].distance + grid[row+1][col].cost
				}
			}
		}
	}
	fmt.Println(grid[99][99].distance)
}

func partTwo() {
	scanner := makeScanner(false)
	width := 100
	scale := 5
	len := width * scale

	grid := [500][500]room{}
	col := 0
	for scanner.Scan() {
		line := scanner.Text()
		for row, v := range line {
			for i := 0; i < scale; i++ {
				for j := 0; j < scale; j++ {
					cost := mustAtoi(string(v)) + i + j
					if cost > 9 {
						cost = ((mustAtoi(string(v)) + i + j) % 10) + 1
					}
					grid[row+i*width][col+j*width] = room{
						row:      row + i*width,
						col:      col + j*width,
						distance: 100000,
						cost:     cost,
					}
				}
			}
		}
		col++
	}
	grid[0][0].distance = 0

	for row := 0; row < len; row++ {
		for col := 0; col < len; col++ {
			// if the cost of the space is less than the current known distance, this is the best route there
			if col+1 < len {
				if grid[row][col+1].distance > grid[row][col+1].cost+grid[row][col].distance {
					grid[row][col+1].distance = grid[row][col].distance + grid[row][col+1].cost
				}
			}
			if row+1 < len {
				if grid[row+1][col].distance > grid[row+1][col].cost+grid[row][col].distance {
					grid[row+1][col].distance = grid[row][col].distance + grid[row+1][col].cost
				}
			}
		}
	}
	fmt.Println(grid[width*scale-1][width*scale-1])
}