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// I'll come back later to this day
//
// The second part is bad with time O(n*(W+H)) -> could be better for sure like O(4n)
package main
import (
"bufio"
"fmt"
"log"
"os"
)
type quadcopter struct {
scans []*scan
}
// Scans all rows and columns, probably could be a bit better
func (q *quadcopter) scanMap(hmap [][]byte, xlen, ylen int) {
for i, row := range hmap {
q.scans[i] = NewScan(row)
}
for y := 0; y < ylen; y++ {
col := make([]byte, xlen)
for x := 0; x < xlen; x++ {
col[x] = hmap[x][y]
}
q.scans[xlen+y] = NewScan(col)
}
}
func (q *quadcopter) countVisibleTrees(hmap [][]byte, xlen, ylen int) int {
// circumference
visible := 2 * (xlen - 1 + ylen - 1)
// inner rectangle
for x := 1; x < xlen-1; x++ {
for y := 1; y < ylen-1; y++ {
tree := hmap[x][y]
xv := q.scans[x].progressScan(tree)
yv := q.scans[xlen+y].progressScan(tree)
if xv {
visible += 1
continue
}
if yv {
visible += 1
continue
}
}
}
return visible
}
type scan struct {
ahead []byte
visited byte
}
func NewScan(trees []byte) *scan {
lastTree := len(trees) - 1
s := scan{
visited: trees[lastTree],
ahead: []byte{trees[lastTree]},
}
// stop before tree[0], it's not in the scan technically
for j := lastTree - 1; j > 0; j-- {
if trees[j] >= s.visited {
s.visited = trees[j]
s.ahead = append(s.ahead, trees[j])
}
}
s.visited = trees[0]
return &s
}
func (s *scan) progressScan(tree byte) bool {
// tree was greatest in scan ahead
if tree == s.ahead[len(s.ahead)-1] {
// keep last tree
if len(s.ahead) > 1 {
s.ahead = s.ahead[:len(s.ahead)-1]
}
}
if tree > s.visited {
s.visited = tree
return true
}
if tree > s.ahead[len(s.ahead)-1] {
return true
}
return false
}
// Could be less repetitive with closures? But go kind of sucks with iterators
func scenicScore(tree byte, hmap [][]byte, x, xlen, y, ylen int) int {
down := 0
for i := x + 1; i < xlen; i++ {
other := hmap[i][y]
down = i - x
if other >= tree {
break
}
}
up := 0
for i := x - 1; i > -1; i-- {
other := hmap[i][y]
up = x - i
if other >= tree {
break
}
}
left := 0
for i := y + 1; i < ylen; i++ {
other := hmap[x][i]
left = i - y
if other >= tree {
break
}
}
right := 0
for i := y - 1; i > -1; i-- {
other := hmap[x][i]
right = y - i
if other >= tree {
break
}
}
return up * down * left * right
}
func main() {
// part 1
f, err := os.Open("day8.txt")
if err != nil {
log.Fatal("Could not open file", err)
}
xlen, ylen := 0, 0
hmap := [][]byte{}
s := bufio.NewScanner(f)
for s.Scan() {
b := s.Bytes()
if ylen == 0 {
ylen = len(b)
}
bcopy := append([]byte(nil), b...)
hmap = append(hmap, bcopy)
xlen += 1
}
q := &quadcopter{
scans: make([]*scan, xlen+ylen),
}
q.scanMap(hmap, xlen, ylen)
vis := q.countVisibleTrees(hmap, xlen, ylen)
fmt.Println("Part 1:", vis)
// part 2
runningScore := 0
for x := 1; x < xlen-1; x++ {
for y := 1; y < ylen-1; y++ {
tree := hmap[x][y]
if s := scenicScore(tree, hmap, x, xlen, y, ylen); s > runningScore {
runningScore = s
}
}
}
fmt.Println("Part 2:", runningScore)
}
|
