57 lines
1.2 KiB
Go
57 lines
1.2 KiB
Go
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package day12
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func FastRunGeneration(plants []byte, rules map[string]byte, rootIndex int) ([]byte, int) {
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newGen := make([]byte, len(plants), len(plants)+4)
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for i := 0; i < len(plants); i++ {
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newGen[i] = rules[getKey(plants, i)]
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}
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result1 := rules[getKey(plants, -2)]
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result2 := rules[getKey(plants, -1)]
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if result1 == '#' || result2 == '#' {
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newGen = append([]byte{result1, result2}, newGen...)
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rootIndex += 2
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}
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result1 = rules[getKey(plants, len(plants))]
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result2 = rules[getKey(plants, len(plants)+1)]
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if result1 == '#' || result2 == '#' {
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newGen = append(newGen, result1, result2)
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}
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return newGen, rootIndex
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}
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func getKey(plants []byte, i int) string {
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if i < 2 {
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key := ""
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for j := 0; j < 2-i; j++ {
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key += "."
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}
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key += string(plants[0 : i+2])
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return key
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}
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if i > len(plants)-2 {
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key := string(plants[i-2 : len(plants)-1])
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for j := 0; j < len(plants)-1-i; j++ {
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key += "."
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}
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key += string(plants[0 : i+2])
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return key
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}
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return string(plants[i-2 : i+2])
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}
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func FastSumPlants(plants []byte, rootIndex int) int {
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sum := 0
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for index, value := range plants {
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if value == '#' {
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sum += index - rootIndex
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}
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}
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return sum
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}
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