2023/go/day06/day06.go

   1 package day06
   2
   3 import (
   4         "fmt"
   5         "math"
   6 )
   7
   8 type Input struct {
   9         Time uint64
  10         Distance uint64
  11 }
  12 func Part1(input string) int {
  13         answer := 1.0
  14         ins := parseInput1(input)
  15         for _, in := range ins {
  16                 t1, t2, _ := solveQuadratic(1, float64(in.Time) * -1, float64(in.Distance))
  17                 fmt.Printf("t1: %v t2: %v ans: %v\n", t1, t2, (t1 - t2 + 1))
  18                 answer *= (t1 - t2 + 1)
  19
  20         }
  21         return int(answer)
  22 }
  23
  24 func Part2(input string) int {
  25         answer := 1.0
  26         ins := parseInput2(input)
  27         for _, in := range ins {
  28                 t1, t2, _ := solveQuadratic(1, float64(in.Time) * -1, float64(in.Distance))
  29                 fmt.Printf("t1: %v t2: %v ans: %v\n", t1, t2, (t1 - t2 + 1))
  30                 answer *= (t1 - t2 + 1)
  31
  32         }
  33         return int(answer)}
  34
  35 func parseInput1(input string) []Input {
  36         var in []Input
  37         in = append(in, Input{46, 214})
  38         in = append(in, Input{80, 1177})
  39         in = append(in, Input{78, 1402})
  40         in = append(in, Input{66, 1024})
  41         return in
  42 }
  43
  44 func parseInput2(input string) []Input {
  45         var in []Input
  46         in = append(in, Input{46807866, 214117714021024})
  47         return in
  48 }
  49
  50 func solveQuadratic(a, b, c float64) (float64, float64, error) {
  51         // Calculate the discriminant
  52         discriminant := b*b - 4*a*c
  53
  54         // Check if the discriminant is non-negative
  55         if discriminant < 0 {
  56                 return 0, 0, fmt.Errorf("no real roots, discriminant is negative")
  57         }
  58
  59         // Calculate the roots
  60         root1 := (-b + math.Sqrt(discriminant)) / (2 * a)
  61         root2 := (-b - math.Sqrt(discriminant)) / (2 * a)
  62
  63         if isWholeNumber(root1) { root1 = root1 - 1.0 }
  64         if isWholeNumber(root2) { root2 = root2 + 1.0 }
  65         return math.Floor(root1), math.Ceil(root2), nil
  66 }
  67
  68 func isWholeNumber(x float64) bool {
  69         rounded := math.Round(x)
  70         return x == rounded
  71 }