advent-of-code/2021/10/second.go

86 lines
1.2 KiB
Go

package main
import (
"bufio"
"fmt"
"os"
"sort"
)
type stack []byte
func (s *stack) clear() {
*s = make(stack, 0)
}
func (s *stack) push(b byte) {
*s = append(*s, b)
}
func (s *stack) pop() *byte {
l := len(*s)
if l == 0 {
return nil
} else {
elt := (*s)[l-1]
*s = (*s)[:l-1]
return &elt
}
}
func main() {
scores := make([]int, 0)
s := make(stack, 0)
scanner := bufio.NewScanner(os.Stdin)
out:
for scanner.Scan() {
line := scanner.Text()
s.clear()
for i := 0; i < len(line); i++ {
c := line[i]
if c == '(' || c == '[' || c == '{' || c == '<' {
s.push(c)
continue
}
b := s.pop()
switch c {
case ')':
if *b != '(' {
continue out
}
case ']':
if *b != '[' {
continue out
}
case '}':
if *b != '{' {
continue out
}
case '>':
if *b != '<' {
continue out
}
}
}
score := 0
for c := s.pop(); c != nil; c = s.pop() {
score *= 5
switch *c {
case '(':
score += 1
case '[':
score += 2
case '{':
score += 3
case '<':
score += 4
}
}
if score != 0 {
scores = append(scores, score)
}
}
sort.Ints(scores)
fmt.Println(scores[len(scores)/2])
}