completed day 6

README.md

@@ -1,7 +1,7 @@
 # Advent of Code 2023
 
 [![Tests](https://github.com/devries/advent_of_code_2023/actions/workflows/main.yml/badge.svg)](https://github.com/devries/advent_of_code_2023/actions/workflows/main.yml)
-[![Stars: 10](https://img.shields.io/badge/⭐_Stars-10-yellow)](https://adventofcode.com/2023)
+[![Stars: 12](https://img.shields.io/badge/⭐_Stars-12-yellow)](https://adventofcode.com/2023)
 
 ## Plan for This Year
 
@@ -81,3 +81,9 @@ opportunity to experiment a bit with code generation.
   do this the number of ranges grows, but it will always be far fewer
   calculations than tracking how each individual element is handled.
 
+- [Day 6: Wait For It](https://adventofcode.com/2023/day/6) - [part 1](day06p1/solution.go), [part 2](day06p2/solution.go)
+
+  This was just solving the quadratic equation for the times when the distance
+  was equal to the time of the race. There was a bit of fiddling with checking
+  if the distance was greater than or equal to the winning distance, but all in
+  all that was the gist of it.

day06p1/solution.go

@@ -0,0 +1,44 @@
+package day06p1
+
+import (
+	"io"
+	"math"
+	"strconv"
+	"strings"
+
+	"aoc/utils"
+)
+
+// 17729182 is too high
+
+func Solve(r io.Reader) any {
+	lines := utils.ReadLines(r)
+
+	timeStrings := strings.Fields(lines[0])
+	distanceStrings := strings.Fields(lines[1])
+
+	sum := 1
+
+	for i := 1; i < len(timeStrings); i++ {
+		time, err := strconv.ParseFloat(timeStrings[i], 64)
+		utils.Check(err, "Unable to parse %s into float", timeStrings[i])
+
+		distance, err := strconv.ParseFloat(distanceStrings[i], 64)
+
+		tPressMin := 0.5*time - 0.5*math.Sqrt(time*time-4.0*distance)
+
+		tPressMax := 0.5*time + 0.5*math.Sqrt(time*time-4.0*distance)
+
+		winways := math.Floor(tPressMax) - math.Ceil(tPressMin)
+		if math.Abs(tPressMin-math.Ceil(tPressMin)) < 1.0e-8 {
+			winways -= 1.0
+		}
+
+		if math.Abs(tPressMax-math.Floor(tPressMax)) < 1.0e-8 {
+			winways -= 1.0
+		}
+
+		sum *= int(winways) + 1
+	}
+	return sum
+}

day06p1/solution_test.go

@@ -0,0 +1,34 @@
+package day06p1
+
+import (
+	"strings"
+	"testing"
+
+	"aoc/utils"
+)
+
+var testInput = `Time:      7  15   30
+Distance:  9  40  200`
+
+func TestSolve(t *testing.T) {
+	tests := []struct {
+		input  string
+		answer int
+	}{
+		{testInput, 288},
+	}
+
+	if testing.Verbose() {
+		utils.Verbose = true
+	}
+
+	for _, test := range tests {
+		r := strings.NewReader(test.input)
+
+		result := Solve(r).(int)
+
+		if result != test.answer {
+			t.Errorf("Expected %d, got %d", test.answer, result)
+		}
+	}
+}

day06p2/solution.go

@@ -0,0 +1,42 @@
+package day06p2
+
+import (
+	"io"
+	"math"
+	"strconv"
+	"strings"
+
+	"aoc/utils"
+)
+
+// 17729182 is too high
+
+func Solve(r io.Reader) any {
+	lines := utils.ReadLines(r)
+
+	timeStrings := strings.Fields(lines[0])
+	distanceStrings := strings.Fields(lines[1])
+
+	timeString := strings.Join(timeStrings[1:], "")
+	distanceString := strings.Join(distanceStrings[1:], "")
+
+	time, err := strconv.ParseFloat(timeString, 64)
+	utils.Check(err, "Unable to parse %s into float", timeString)
+
+	distance, err := strconv.ParseFloat(distanceString, 64)
+
+	tPressMin := 0.5*time - 0.5*math.Sqrt(time*time-4.0*distance)
+
+	tPressMax := 0.5*time + 0.5*math.Sqrt(time*time-4.0*distance)
+
+	winways := math.Floor(tPressMax) - math.Ceil(tPressMin)
+	if math.Abs(tPressMin-math.Ceil(tPressMin)) < 1.0e-8 {
+		winways -= 1.0
+	}
+
+	if math.Abs(tPressMax-math.Floor(tPressMax)) < 1.0e-8 {
+		winways -= 1.0
+	}
+
+	return int(winways) + 1
+}

day06p2/solution_test.go

@@ -0,0 +1,34 @@
+package day06p2
+
+import (
+	"strings"
+	"testing"
+
+	"aoc/utils"
+)
+
+var testInput = `Time:      7  15   30
+Distance:  9  40  200`
+
+func TestSolve(t *testing.T) {
+	tests := []struct {
+		input  string
+		answer int
+	}{
+		{testInput, 71503},
+	}
+
+	if testing.Verbose() {
+		utils.Verbose = true
+	}
+
+	for _, test := range tests {
+		r := strings.NewReader(test.input)
+
+		result := Solve(r).(int)
+
+		if result != test.answer {
+			t.Errorf("Expected %d, got %d", test.answer, result)
+		}
+	}
+}