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package main
import (
"fmt"
"os"
"strings"
)
func main() {
content, err := os.ReadFile("data.txt")
if err != nil {
panic(err)
}
fmt.Println(part1("xmul(2,4)%&mul[3,7]!@^do_not_mul(5,5)+mul(32,64]then(mul(11,8)mul(8,5))"))
fmt.Println(part1(string(content)))
fmt.Println(part2("xmul(2,4)&mul[3,7]!^don't()_mul(5,5)+mul(32,64](mul(11,8)undo()?mul(8,5))"))
fmt.Println(part2(string(content)))
}
func part1(s string) (result int) {
for {
index := strings.Index(s, "mul(")
if index < 0 {
return
}
s = s[index+4:]
op1, opLength := parseOperand(&s)
if opLength < 1 || opLength > 3 {
continue
}
if !expectChar(&s, ',') {
continue
}
op2, opLength := parseOperand(&s)
if opLength < 1 || opLength > 3 {
continue
}
if !expectChar(&s, ')') {
continue
}
result += op1 * op2
}
}
func part2(s string) (result int) {
for {
dont_index := strings.Index(s, "don't()")
if dont_index < 0 {
result += part1(s)
return
}
result += part1(s[:dont_index])
s = s[dont_index+7:]
do_index := strings.Index(s, "do()")
if do_index < 0 {
return
}
s = s[do_index+4:]
}
return
}
func expectChar(s *string, r byte) bool {
if len(*s) == 0 || (*s)[0] != r {
return false
} else {
*s = (*s)[1:]
return true
}
}
func parseOperand(s *string) (operand int, length int) {
for len(*s) > 0 {
c := (*s)[0]
if c < '0' || c > '9' {
return
}
operand = operand*10 + int(c-'0')
*s = (*s)[1:]
length++
}
return
}
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