81 lines
1.5 KiB
Go
81 lines
1.5 KiB
Go
package main
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import (
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"bufio"
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"fmt"
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"os"
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"slices"
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"strconv"
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)
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func main() {
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fmt.Println(part1([]int64{1, 10, 100, 2024}), 37327623)
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fmt.Println(part1(readData("data.txt")), 13004408787)
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fmt.Println(part2([]int64{1, 2, 3, 2024}), 23)
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fmt.Println(part2(readData("data.txt")))
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}
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func part1(init []int64) (result int64) {
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for _, n := range init {
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for range 2000 {
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n = next(n)
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}
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result += n
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}
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return
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}
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func makeChangeId(memory [4]int, i int) (result int) {
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for j := range 4 {
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result = result*19 + memory[(i+j)%4] + 9
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}
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return
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}
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func part2(init []int64) int {
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priceForChangeId := make([]int, 19*19*19*19)
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for _, n := range init {
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seenChange := make([]bool, 19*19*19*19)
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prevPrice := n % 10
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memory := [4]int{0, 0, 0, 0}
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for i := range 2000 {
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n2 := next(n)
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price := n2 % 10
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change := price - prevPrice
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memory[i%4] = int(change)
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if i >= 3 {
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changeId := makeChangeId(memory, i)
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if !seenChange[changeId] {
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seenChange[changeId] = true
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priceForChangeId[changeId] += int(price)
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}
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}
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n, prevPrice = n2, price
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}
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}
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return slices.Max(priceForChangeId)
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}
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func prune(a int64) int64 {
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return a % 16777216
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}
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func next(a int64) int64 {
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a = prune((a << 6) ^ a)
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a = prune((a >> 5) ^ a)
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a = prune((a << 11) ^ a)
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return a
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}
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func readData(fileName string) (numbers []int64) {
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fp, _ := os.Open(fileName)
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scanner := bufio.NewScanner(fp)
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for scanner.Scan() {
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n, _ := strconv.ParseInt(scanner.Text(), 10, 64)
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numbers = append(numbers, n)
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}
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return
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}
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