adventofcode/2023/day22/main.go

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package main
import (
"fmt"
"sort"
"strings"
h "git.bullercodeworks.com/brian/adventofcode/helpers"
)
func main() {
inp := h.StdinToStringSlice()
part1(inp)
fmt.Println()
part2(inp)
}
func part1(input []string) {
var bricks [][]int
for _, line := range input {
values := strings.Split(strings.ReplaceAll(line, "~", ","), ",")
var brick []int
for _, v := range values {
num := 0
fmt.Sscanf(v, "%d", &num)
brick = append(brick, num)
}
bricks = append(bricks, brick)
}
sort.Slice(bricks, func(i, j int) bool {
return bricks[i][2] < bricks[j][2]
})
for index, brick := range bricks {
maxZ := 1
for _, check := range bricks[:index] {
if overlaps(brick, check) {
maxZ = max(maxZ, check[5]+1)
}
}
brick[5] -= brick[2] - maxZ
brick[2] = maxZ
}
sort.Slice(bricks, func(i, j int) bool {
return bricks[i][2] < bricks[j][2]
})
kSupportsV := make(map[int]map[int]struct{})
vSupportsK := make(map[int]map[int]struct{})
for i := range bricks {
kSupportsV[i] = make(map[int]struct{})
vSupportsK[i] = make(map[int]struct{})
}
for j, upper := range bricks {
for i, lower := range bricks[:j] {
if overlaps(lower, upper) && upper[2] == lower[5]+1 {
kSupportsV[i][j] = struct{}{}
vSupportsK[j][i] = struct{}{}
}
}
}
total := 0
for i := range bricks {
satisfies := true
for j := range kSupportsV[i] {
if len(vSupportsK[j]) < 2 {
satisfies = false
break
}
}
if satisfies {
total++
}
}
fmt.Println("# Part 1")
fmt.Println(total)
}
func part2(input []string) {
var bricks [][]int
for _, line := range input {
values := strings.Split(strings.ReplaceAll(line, "~", ","), ",")
var brick []int
for _, v := range values {
num := 0
fmt.Sscanf(v, "%d", &num)
brick = append(brick, num)
}
bricks = append(bricks, brick)
}
sort.SliceStable(bricks, func(i, j int) bool {
return bricks[i][2] < bricks[j][2]
})
for index, brick := range bricks {
maxZ := 1
for _, check := range bricks[:index] {
if overlaps(brick, check) {
maxZ = max(maxZ, check[5]+1)
}
}
brick[5] -= brick[2] - maxZ
brick[2] = maxZ
}
sort.SliceStable(bricks, func(i, j int) bool {
return bricks[i][2] < bricks[j][2]
})
kSupportsV := make(map[int]map[int]struct{})
vSupportsK := make(map[int]map[int]struct{})
for i := range bricks {
kSupportsV[i] = make(map[int]struct{})
vSupportsK[i] = make(map[int]struct{})
}
for j, upper := range bricks {
for i, lower := range bricks[:j] {
if overlaps(lower, upper) && upper[2] == lower[5]+1 {
kSupportsV[i][j] = struct{}{}
vSupportsK[j][i] = struct{}{}
}
}
}
total := 0
for i := range bricks {
q := make([]int, 0)
for j := range kSupportsV[i] {
if len(vSupportsK[j]) == 1 {
q = append(q, j)
}
}
falling := make(map[int]struct{})
for _, j := range q {
falling[j] = struct{}{}
}
falling[i] = struct{}{}
for len(q) > 0 {
j := q[0]
q = q[1:]
for k := range kSupportsV[j] {
if _, ok := falling[k]; !ok {
if isSubset(vSupportsK[k], falling) {
q = append(q, k)
falling[k] = struct{}{}
}
}
}
}
total += len(falling) - 1
}
fmt.Println("# Part 2")
fmt.Println(total)
}
func isSubset(set1, set2 map[int]struct{}) bool {
for key := range set1 {
if _, ok := set2[key]; !ok {
return false
}
}
return true
}
func overlaps(a, b []int) bool {
return max(a[0], b[0]) <= min(a[3], b[3]) && max(a[1], b[1]) <= min(a[4], b[4])
}
func max(a, b int) int {
if a > b {
return a
}
return b
}
func min(a, b int) int {
if a < b {
return a
}
return b
}