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18.go
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18.go
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package main
import (
"fmt"
"io/ioutil"
"regexp"
"strconv"
"strings"
)
func parseInput() []byte {
input, err := ioutil.ReadFile("input.txt")
if err != nil {
panic(err)
}
return input
}
var newLine = "\r\n"
func prepInput(input []byte) []string {
lines := strings.Split(strings.TrimSpace(string(input)), newLine)
return lines
}
func main() {
lines := prepInput(parseInput())
part1, part2 := 0, 0
re := regexp.MustCompile(`\([^\(\)]+\)`)
for _, line := range lines {
part1 += resolveExprFunc(line, samePrecedence, re)
part2 += resolveExprFunc(line, inversePrecedence, re)
}
fmt.Println(part1)
fmt.Println(part2)
}
func resolveExprFunc(line string, fn func(string) int, re *regexp.Regexp) int {
for re.MatchString(line) {
line = re.ReplaceAllStringFunc(line, func(line string) string { return strconv.Itoa(fn(line)) })
}
return fn(line)
}
func samePrecedence(expr string) int {
parts := strings.Fields(strings.Trim(expr, "()"))
res, _ := strconv.Atoi(parts[0])
for i := 1; i < len(parts); i += 2 {
val, _ := strconv.Atoi(parts[i+1])
switch parts[i] {
case "+":
res += val
case "*":
res *= val
}
}
return res
}
func inversePrecedence(expr string) int {
return resolveExprFunc(expr, samePrecedence, regexp.MustCompile(`\d+ \+ \d+`))
}