day13

day13p1/solution.go

@@ -0,0 +1,41 @@
+package day13p1
+
+import (
+	"io"
+	"regexp"
+	"strconv"
+
+	"aoc/utils"
+)
+
+func Solve(r io.Reader) any {
+	lines := utils.ReadLines(r)
+	numregex := regexp.MustCompile(`\d+`)
+
+	// create blocks - blocks are 3 lines (until \n)
+	blocks := make([]string, 0)
+	for i := 0; i < len(lines); i += 4 {
+		blocks = append(blocks, lines[i]+"\n"+lines[i+1]+"\n"+lines[i+2])
+	}
+
+	sum := 0
+
+	for _, block := range blocks {
+		resultsStr := numregex.FindAllString(block, -1)
+		// convert to int
+		results := make([]int, len(resultsStr))
+		for i, r := range resultsStr {
+			results[i], _ = strconv.Atoi(r)
+		}
+		ax, ay, bx, by, px, py := results[0], results[1], results[2], results[3], results[4], results[5]
+		// i got this by making an equation system
+		denom := ax*by - ay*bx
+		a := (px*by - py*bx) / denom
+		b := (ax*py - ay*px) / denom
+		if ax*a+bx*b == px && ay*a+by*b == py {
+			sum += a*3 + b
+		}
+	}
+
+	return sum
+}

day13p1/solution_test.go

@@ -0,0 +1,47 @@
+package day13p1
+
+import (
+	"strings"
+	"testing"
+
+	"aoc/utils"
+)
+
+var testInput = `Button A: X+94, Y+34
+Button B: X+22, Y+67
+Prize: X=8400, Y=5400
+
+Button A: X+26, Y+66
+Button B: X+67, Y+21
+Prize: X=12748, Y=12176
+
+Button A: X+17, Y+86
+Button B: X+84, Y+37
+Prize: X=7870, Y=6450
+
+Button A: X+69, Y+23
+Button B: X+27, Y+71
+Prize: X=18641, Y=10279`
+
+func TestSolve(t *testing.T) {
+	tests := []struct {
+		input  string
+		answer int
+	}{
+		{testInput, 480},
+	}
+
+	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)
+		}
+	}
+}

day13p2/solution.go

@@ -0,0 +1,43 @@
+package day13p2
+
+import (
+	"io"
+	"regexp"
+	"strconv"
+
+	"aoc/utils"
+)
+
+func Solve(r io.Reader) any {
+	lines := utils.ReadLines(r)
+	numregex := regexp.MustCompile(`\d+`)
+
+	// create blocks - blocks are 3 lines (until \n)
+	blocks := make([]string, 0)
+	for i := 0; i < len(lines); i += 4 {
+		blocks = append(blocks, lines[i]+"\n"+lines[i+1]+"\n"+lines[i+2])
+	}
+
+	sum := 0
+
+	for _, block := range blocks {
+		resultsStr := numregex.FindAllString(block, -1)
+		// convert to int
+		results := make([]int, len(resultsStr))
+		for i, r := range resultsStr {
+			results[i], _ = strconv.Atoi(r)
+		}
+		ax, ay, bx, by, px, py := results[0], results[1], results[2], results[3], results[4], results[5]
+		px += 10000000000000
+		py += 10000000000000
+		// i got this by making an equation system
+		denom := ax*by - ay*bx
+		a := (px*by - py*bx) / denom
+		b := (ax*py - ay*px) / denom
+		if ax*a+bx*b == px && ay*a+by*b == py {
+			sum += a*3 + b
+		}
+	}
+
+	return sum
+}

day13p2/solution_test.go

@@ -0,0 +1,47 @@
+package day13p2
+
+import (
+	"strings"
+	"testing"
+
+	"aoc/utils"
+)
+
+var testInput = `Button A: X+94, Y+34
+Button B: X+22, Y+67
+Prize: X=8400, Y=5400
+
+Button A: X+26, Y+66
+Button B: X+67, Y+21
+Prize: X=12748, Y=12176
+
+Button A: X+17, Y+86
+Button B: X+84, Y+37
+Prize: X=7870, Y=6450
+
+Button A: X+69, Y+23
+Button B: X+27, Y+71
+Prize: X=18641, Y=10279`
+
+func TestSolve(t *testing.T) {
+	tests := []struct {
+		input  string
+		answer int
+	}{
+		{testInput, 875318608908},
+	}
+
+	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)
+		}
+	}
+}