151 lines
1.9 KiB
Go
151 lines
1.9 KiB
Go
package main
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import (
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"AoC/2021/common"
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"bufio"
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"strconv"
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)
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func main() {
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part1()
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part2()
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}
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func part1() {
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aoc := aoc.New(2021, 3)
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aoc.Test(`
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00100
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11110
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10110
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10111
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10101
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01111
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00111
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11100
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10000
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11001
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00010
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01010
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`, 198)
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aoc.Solution(func (input *bufio.Scanner) int {
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length := 0
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var entries []int
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for input.Scan() {
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line := input.Text()
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if len(line) > length {
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length = len(line)
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}
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num, err := strconv.ParseInt(line, 2, 64)
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if err != nil {
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panic(err)
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}
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entries = append(entries, int(num))
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}
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gamma := 0
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epsilon := 0
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for j := 0; j < length; j++ {
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var count int
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for _, num := range entries {
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count += num >> j & 1
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}
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if float64(count)/float64(len(entries)) >= 0.5 {
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gamma += 1 << j
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} else {
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epsilon += 1 << j
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}
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}
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return gamma*epsilon
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})
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}
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func filter(entries []int, length int, findCommon bool) int {
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e := make([]int, len(entries))
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copy(e, entries)
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for j := length-1; j >= 0; j-- {
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var count int
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for _, num := range e {
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count += num >> j & 1
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}
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var common int
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if !findCommon {
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common = 1
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}
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if float64(count)/float64(len(e)) >= 0.5 {
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if findCommon {
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common = 1
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} else {
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common = 0
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}
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}
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n := 0
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for _, num := range e {
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if num >> j & 1 == common {
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e[n] = num
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n++
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}
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}
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e = e[:n]
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if len(e) == 1 {
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break
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}
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}
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return e[0]
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}
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func part2() {
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aoc := aoc.New(2021, 3)
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aoc.Test(`
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00100
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11110
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10110
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10111
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10101
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01111
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00111
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11100
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10000
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11001
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00010
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01010
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`, 230)
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aoc.Solution(func (input *bufio.Scanner) int {
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length := 0
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var entries []int
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for input.Scan() {
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line := input.Text()
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if len(line) > length {
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length = len(line)
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}
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num, err := strconv.ParseInt(line, 2, 64)
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if err != nil {
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panic(err)
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}
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entries = append(entries, int(num))
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}
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oxygen := filter(entries, length, true)
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co2 := filter(entries, length, false)
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return int(oxygen * co2)
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})
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}
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