80 lines
1.7 KiB
Go
80 lines
1.7 KiB
Go
package d3
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import (
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"strconv"
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"strings"
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)
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func D3(input string) int64 {
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binaries := strings.Split(strings.TrimSpace(input), "\n")
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ones := make([]int, len(binaries[0]))
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for _, binary := range binaries {
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for position, bit := range binary {
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if byte(bit) == '1' {
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ones[position]++
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}
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}
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}
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gamma := make([]string, len(ones))
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epsilon := make([]string, len(ones))
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for pos, oneCount := range ones {
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if oneCount > len(binaries)/2 {
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gamma[pos] = "1"
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epsilon[pos] = "0"
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} else {
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gamma[pos] = "0"
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epsilon[pos] = "1"
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}
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}
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gammaNum, _ := strconv.ParseInt(strings.Join(gamma, ""), 2, 64)
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epsilonNum, _ := strconv.ParseInt(strings.Join(epsilon, ""), 2, 64)
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return gammaNum * epsilonNum
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}
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func rating(binaries []string, position int, path func([]string, []string) []string) string {
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if len(binaries) == 1 {
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return binaries[0]
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}
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ones := make([]string, 0, len(binaries)/2) // allocate at least half original slice
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zeroes := make([]string, 0, len(binaries)/2)
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for _, binary := range binaries {
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if binary[position] == '1' {
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ones = append(ones, binary)
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} else {
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zeroes = append(zeroes, binary)
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}
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}
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return rating(path(ones, zeroes), position+1, path)
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}
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func D3P2(input string) int64 {
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binaries := strings.Split(strings.TrimSpace(input), "\n")
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o2predicate := func(ones, zeroes []string) []string {
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if len(ones) == len(zeroes) || len(ones) > len(zeroes) {
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return ones
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}
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return zeroes
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}
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co2predicate := func(ones, zeroes []string) []string {
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if len(ones) == len(zeroes) || len(ones) > len(zeroes) {
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return zeroes
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}
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return ones
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}
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o2rating, _ := strconv.ParseInt(rating(binaries, 0, o2predicate), 2, 64)
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co2rating, _ := strconv.ParseInt(rating(binaries, 0, co2predicate), 2, 64)
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return o2rating * co2rating
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}
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