77 lines
2.0 KiB
Go
77 lines
2.0 KiB
Go
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package day_01
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import (
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"fmt"
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"sort"
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"strings"
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)
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// task:https://adventofcode.com/2024/day/1
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// short summary - we are offered two lists of location IDs,
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// and we need to compare the smallest ID from one list with the
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// smallest from the other one,
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// and calculate the difference between them
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func SolveBasic(input string) int {
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firstIds, secondIds := loadSortedLocationIds(input)
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diff := 0
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for i := 0; i < len(firstIds); i++ {
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diff += abs(firstIds[i] - secondIds[i])
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}
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return diff
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}
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// task:https://adventofcode.com/2024/day/1#part2
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// short summary - the initial comparison wasn't that good,
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// so instead we need to check how often values
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// from the first list appear in the second one, multiply the value with the number
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// of appearances and sum all of that up
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func SolveComplex(input string) int {
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firstIds, secondIds := loadSortedLocationIds(input)
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// we could have avoided this and run a binary search and count for every number
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// but this was simpler and perhaps even faster to run
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idOccurrences := map[int]int{}
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for _, locationId := range secondIds {
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// this works for missing values as idOccurrences[location]
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// will return 0 if no value is present for numbers
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idOccurrences[locationId] = idOccurrences[locationId] + 1
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}
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sum := 0
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for _, locationId := range firstIds {
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// this works for the same reason as above
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sum += idOccurrences[locationId] * locationId
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}
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return sum
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}
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// helper methods
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func loadSortedLocationIds(input string) ([]int, []int) {
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lines := strings.Split(input, "\n")
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// we create slices of the required size at start
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firstIds := make([]int, len(lines))
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secondIds := make([]int, len(lines))
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for i, line := range lines {
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if _, err := fmt.Sscan(line, &firstIds[i], &secondIds[i]); err != nil {
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panic(err)
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}
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}
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sort.Ints(firstIds)
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sort.Ints(secondIds)
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return firstIds, secondIds
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}
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// go doesn't have an Abs(int) int func so we write our own
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func abs(value int) int {
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if value < 0 {
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return -value
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}
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return value
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}
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