94 lines
1.8 KiB
Go
94 lines
1.8 KiB
Go
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package main
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import (
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"os"
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"fmt"
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"strconv"
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"strings"
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)
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// general util
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func check(e error) {
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if e != nil { panic(e) }
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}
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func pop(arr []int, index *int) int {
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/* get last element that is not a -1 and replacing it with -1 int the source slice */
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for i := len(arr) - 1; i >= 0; i-- {
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if arr[i] != -1 {
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(*index) = i
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elem := arr[i]
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arr[i] = -1
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return elem
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}
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}
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return -1
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}
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func insert(arr []int, n int) int {
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/* insert element at the first -1, return the index of this -1 */
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for i, elem := range arr {
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if elem == -1 {
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arr[i] = n
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return i
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}
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}
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return -1
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}
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// main loop
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func main() {
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// read in file
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dat, err := os.ReadFile("data.txt")
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check(err)
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dat_str := strings.TrimSpace(string(dat))
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// contruct input as int arr
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input := make([]int, 0, len(dat_str))
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mem_size := 0
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for _, char := range []rune(dat_str) {
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num, err := strconv.Atoi(string(char))
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check(err)
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mem_size += num
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input = append(input, num)
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}
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// convert to actual memory representation
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mem := make([]int, 0, mem_size)
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is_file := true
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file_id := 0
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for _, elem := range input {
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if is_file {
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for range elem {
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mem = append(mem, file_id)
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}
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file_id++
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} else {
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for range elem {
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mem = append(mem, -1)
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}
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}
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is_file = !is_file
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}
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// reorder
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idx_pop := -1
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idx_insert := -2
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for idx_pop != idx_insert {
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elem := pop(mem, &idx_pop)
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idx_insert = insert(mem, elem)
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}
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// calc checksum
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checksum := 0
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for i, elem := range mem {
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if elem == -1 { break }
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checksum += i * elem
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}
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fmt.Println(checksum)
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}
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