1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
|
// 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... meh not sure how to optimize this further? Each tree can have local best scenic score
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)
}
|
