AdventOfCode2023/03/main.go

191 lines
3.9 KiB
Go

package main
import (
"bufio"
"fmt"
"os"
"strconv"
"time"
)
func mustAtoi(line []rune) int {
i, _ := strconv.Atoi(string(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 schematic map[coord]entry
type entry struct {
num []rune
symb rune
}
type coord struct {
row int
col int
}
func isSymbol(s schematic, row, col int) bool {
if c, ok := s[coord{row, col}]; ok {
return c.symb != 0
}
return false
}
func partOne() {
scanner := makeScanner(false)
row := 0
schematic := schematic{}
// read the whole thing in
for scanner.Scan() {
line := scanner.Text()
acc := []rune{}
for col, c := range line {
switch c {
case '1', '2', '3', '4', '5', '6', '7', '8', '9', '0':
acc = append(acc, c)
default:
if len(acc) != 0 {
schematic[coord{row, col - len(acc)}] = entry{num: acc}
acc = []rune{}
}
if c != '.' {
schematic[coord{row, col}] = entry{symb: c}
}
}
}
// check if we have a number still to save but ran out of line
if len(acc) != 0 {
schematic[coord{row, len(line) - len(acc)}] = entry{num: acc}
}
row++
}
sum := 0
// now, map back over the schematics and find the parts
for row := 0; row <= 139; row++ {
for col := 0; col <= 139; col++ {
if entry, ok := schematic[coord{row, col}]; ok && entry.symb == 0 {
part := mustAtoi(entry.num)
if isSymbol(schematic, row, col-1) {
// look behind
sum += part
}
if isSymbol(schematic, row, col+len(entry.num)) {
// look ahead
sum += part
}
for i := -1; i < len(entry.num)+1; i++ {
// check row above and below
if isSymbol(schematic, row-1, col+i) {
sum += part
}
if isSymbol(schematic, row+1, col+i) {
sum += part
}
}
}
}
}
fmt.Println(sum)
}
func partTwo() {
scanner := makeScanner(false)
row := 0
schematic := schematic{}
// read the whole thing in
for scanner.Scan() {
line := scanner.Text()
acc := []rune{}
for col, c := range line {
switch c {
case '1', '2', '3', '4', '5', '6', '7', '8', '9', '0':
acc = append(acc, c)
default:
if len(acc) != 0 {
schematic[coord{row, col - len(acc)}] = entry{num: acc}
acc = []rune{}
}
if c == '*' { // no longer care about other symbols
schematic[coord{row, col}] = entry{symb: c}
}
}
}
// check if we have a number still to save but ran out of line
if len(acc) != 0 {
schematic[coord{row, len(line) - len(acc)}] = entry{num: acc}
}
row++
}
gears := map[coord]int{}
sum := 0
// map back over the schematics and find the gears.
// there are only ever 1 or 2 parts attached to a gear.
for row := 0; row <= 139; row++ {
for col := 0; col <= 139; col++ {
if entry, ok := schematic[coord{row, col}]; ok && entry.symb == 0 {
offset := len(entry.num)
part := mustAtoi(entry.num)
if isSymbol(schematic, row, col-1) {
k := coord{row, col - 1}
if gears[k] != 0 {
sum += gears[k] * part
} else {
gears[k] = part
}
}
if isSymbol(schematic, row, col+offset) {
k := coord{row, col + offset}
if gears[k] != 0 {
sum += gears[k] * part
} else {
gears[k] = part
}
}
for i := -1; i < offset+1; i++ {
if isSymbol(schematic, row-1, col+i) {
k := coord{row - 1, col + i}
if gears[k] != 0 {
sum += gears[k] * part
} else {
gears[k] = part
}
}
if isSymbol(schematic, row+1, col+i) {
k := coord{row + 1, col + i}
if gears[k] != 0 {
sum += gears[k] * part
} else {
gears[k] = part
}
}
}
}
}
}
fmt.Println(sum)
}