aoc-2022/day9/solution.go

package day9

import (
	"fmt"
	"math"
	"strconv"
	"strings"
)

type Solver struct {
	moves []Move
}

type Location struct {
	r, c int
}

func (l *Location) String() string {
	return fmt.Sprintf("[%3d,%3d]", l.r, l.c)
}

type Move struct {
	direction string
	count     int
}

func (s *Solver) ParseInput(input []string) {
	s.moves = make([]Move, len(input))
	for i, l := range input {
		x := strings.Split(l, " ")
		v, _ := strconv.Atoi(x[1])
		s.moves[i] = Move{x[0], v}
	}
	//fmt.Println(s.moves)
}

func sign(i int) int {
	if i == 0 {
		return 0
	} else if i > 0 {
		return 1
	} else {
		return -1
	}
}

func (s *Solver) SolvePart1() any {
	headLoc := Location{0, 0}
	tailLoc := Location{0, 0}

	locMap := make(map[Location]bool)
	locMap[tailLoc] = true

	for _, m := range s.moves {
		for i := 0; i < m.count; i++ {
			switch m.direction {
			case "R":
				headLoc = Location{headLoc.r, headLoc.c + 1}
			case "L":
				headLoc = Location{headLoc.r, headLoc.c - 1}
			case "U":
				headLoc = Location{headLoc.r + 1, headLoc.c}
			case "D":
				headLoc = Location{headLoc.r - 1, headLoc.c}
			}
			dr, dc := tailLoc.r-headLoc.r, tailLoc.c-headLoc.c
			if math.Abs(float64(dr)) > 1 || math.Abs(float64(dc)) > 1 {
				tailLoc = Location{tailLoc.r - sign(dr), tailLoc.c - sign(dc)}
			}

			locMap[tailLoc] = true
			//fmt.Printf("dr: %d, dc: %d\n", dr, dc)
			//fmt.Printf("H: %v, T: %v\n", headLoc, tailLoc)
		}
	}

	return len(locMap)
}

func (s *Solver) SolvePart2() any {
	ropeLocs := make([]*Location, 10)
	for i := 0; i < len(ropeLocs); i++ {
		ropeLocs[i] = &Location{}
	}

	locMap := make(map[Location]bool)
	locMap[*ropeLocs[len(ropeLocs)-1]] = true

	//fmt.Printf("%s\n", ropeLocs)

	for _, m := range s.moves {
		for i := 0; i < m.count; i++ {
			switch m.direction {
			case "R":
				ropeLocs[0].c++
			case "L":
				ropeLocs[0].c--
			case "U":
				ropeLocs[0].r--
			case "D":
				ropeLocs[0].r++
			}

			for ropeSegmentInd := 1; ropeSegmentInd < len(ropeLocs); ropeSegmentInd++ {
				this := ropeLocs[ropeSegmentInd]
				parent := ropeLocs[ropeSegmentInd-1]

				dr, dc := this.r-parent.r, this.c-parent.c

				if math.Abs(float64(dr)) > 1 || math.Abs(float64(dc)) > 1 {
					this.r -= sign(dr)
					this.c -= sign(dc)
				}
			}
			locMap[*ropeLocs[len(ropeLocs)-1]] = true
			//fmt.Printf("dr: %d, dc: %d\n", dr, dc)
		}
		//printRope(ropeLocs)
		//fmt.Printf("%s\n", ropeLocs)
	}

	return len(locMap)
}

func printRope(locs []*Location) {
	//minC, maxC, minR, maxR := -15, 15, -15, 15
	minC, maxC, minR, maxR := 0, 0, 0, 0

	for _, l := range locs {
		if l.c < minC {
			minC = l.c
		}
		if l.c > maxC {
			maxC = l.c
		}
		if l.r < minR {
			minR = l.r
		}
		if l.r > maxR {
			maxR = l.r
		}
	}

	//println(maxR, minR, maxC, minC)

	field := make([][]byte, maxR-minR+1)
	for i := 0; i < len(field); i++ {
		field[i] = make([]byte, maxC-minC+1)
		for j := 0; j < len(field[i]); j++ {
			field[i][j] = '.'
		}
	}

	field[-minR][-minC] = 's'

	for i := len(locs) - 1; i >= 0; i-- {
		loc := locs[i]
		if i == 0 {
			field[loc.r-minR][loc.c-minC] = 'H'
		} else {
			field[loc.r-minR][loc.c-minC] = '0' + byte(i)
		}
	}

	for _, l := range field {
		fmt.Println(string(l))
	}
	fmt.Println()
}