103 lines
2.0 KiB
Go
103 lines
2.0 KiB
Go
package main
|
|
|
|
import (
|
|
"bufio"
|
|
"fmt"
|
|
"os"
|
|
"strconv"
|
|
"time"
|
|
)
|
|
|
|
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)
|
|
}
|
|
|
|
func partOne() {
|
|
scanner := makeScanner(false)
|
|
|
|
r := map[int]int64{} // index => count of 1s
|
|
var lines int64
|
|
|
|
for scanner.Scan() {
|
|
line := scanner.Text()
|
|
lines++
|
|
n, _ := strconv.ParseInt(line, 2, 64)
|
|
for i := 0; i < len(line); i++ {
|
|
// add the number (1 or 0) in the i'th place to r[i]
|
|
r[i] += (n & (1 << i)) >> i
|
|
}
|
|
}
|
|
var epsilon, gamma int64
|
|
for i, b := range r {
|
|
// if more than half the bits were ones, gamma gets the 1, otherwise epsilon gets the 1
|
|
// alternatively, this could have been an XOR operation, I suppose, once one or the other had been computed
|
|
if b > lines/2 {
|
|
gamma += 1 << i
|
|
} else {
|
|
epsilon += 1 << i
|
|
}
|
|
}
|
|
fmt.Println(epsilon * gamma)
|
|
}
|
|
|
|
func partTwo() {
|
|
scanner := makeScanner(false)
|
|
|
|
inputs := []int64{}
|
|
var oxgen, co2scrub int64
|
|
|
|
var bitlen int
|
|
for scanner.Scan() {
|
|
line := scanner.Text()
|
|
if bitlen == 0 {
|
|
bitlen = len(line)
|
|
}
|
|
n, _ := strconv.ParseInt(line, 2, 64)
|
|
inputs = append(inputs, n)
|
|
}
|
|
|
|
// on initial loop, oxgen>>i == n>>i etc always come out to 0 == 0
|
|
for i := bitlen; i > 0; i-- {
|
|
var oxOnes, oxZeroes, coOnes, coZeroes int64
|
|
for _, n := range inputs {
|
|
if oxgen>>i == n>>i {
|
|
if oxgen>>(i-1)^n>>(i-1) == 1 {
|
|
oxOnes++
|
|
} else {
|
|
oxZeroes++
|
|
}
|
|
}
|
|
if co2scrub>>i == n>>i {
|
|
if co2scrub>>(i-1)^n>>(i-1) == 1 {
|
|
coOnes++
|
|
} else {
|
|
coZeroes++
|
|
}
|
|
}
|
|
}
|
|
if oxOnes >= oxZeroes {
|
|
oxgen += (1 << (i - 1))
|
|
}
|
|
if (coZeroes == 0 && coOnes != 0) || (coOnes < coZeroes && coOnes != 0) {
|
|
co2scrub += (1 << (i - 1))
|
|
}
|
|
}
|
|
fmt.Println(oxgen * co2scrub)
|
|
}
|