80 lines
1.6 KiB
Go
80 lines
1.6 KiB
Go
package day6
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import (
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"fmt"
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"log"
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"os"
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"strconv"
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"strings"
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)
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func Run() int {
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input := ReadInput("day6/input")
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result := 1
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for _, race := range input {
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result *= race.countWinningMoves()
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}
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log.Printf("input %+v\n", input)
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return result
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}
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type Race struct {
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Time, Target int
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}
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func (r Race) countWinningMoves() int {
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// oh and it's simmetrical
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leftPad := 0
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rightPad := 0
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for i := 0; i < (r.Time / 2 + 1); i++ {
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if i * (r.Time - i) > r.Target {
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leftPad = i
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break
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}
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}
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for i := 0; i < (r.Time / 2 + 1); i++ {
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time := r.Time - i
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if time * (r.Time - time) > r.Target {
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rightPad = i
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break
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}
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}
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result := r.Time + 1 - leftPad - rightPad
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log.Printf("for race %+v got left %d and right %d for total wind %d\n", r, leftPad, rightPad, result)
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return result
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}
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func ReadInput(filename string) []Race {
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result := make([]Race, 0)
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bytes, err := os.ReadFile(filename)
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if err != nil {
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panic(fmt.Sprintln("problem readin input : ", filename))
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}
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text := strings.Split( string(bytes), "\n")
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times := strings.Fields(text[0])
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distances := strings.Fields(text[1])
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for i := 1; i < len(times); i++ {
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time, err1 := strconv.Atoi(times[i])
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target, err2 := strconv.Atoi(distances[i])
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if err1 != nil || err2 != nil {
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panic(fmt.Sprintf("error reading race %d from %s %s\n", i, times[i], distances[i]))
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}
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race := Race{
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Time: time,
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Target: target,
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}
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result = append(result, race)
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}
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return result
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}
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// my guess is that i can search from start and end into middle and stop when i find solution
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// from the way i think derivation of x*y works
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// but first - read in the input. with strings.Fields should be easy
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