lol, day 17 is just spamming every possible arc

17/main.go

@@ -0,0 +1,159 @@
+package main
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strconv"
+	"time"
+)
+
+func mustAtoi(line string) int {
+	i, _ := strconv.Atoi(line)
+	return i
+}
+
+func main() {
+	start := time.Now()
+	partOne()
+	duration := time.Since(start)
+	partTwo()
+	duration2 := time.Since(start)
+	fmt.Printf("p1: %s, p2: %s\n", duration, duration2-duration)
+}
+
+func makeScanner(test bool) *bufio.Scanner {
+	var f *os.File
+	if test {
+		f, _ = os.Open("inputs/testinput")
+	} else {
+		f, _ = os.Open("inputs/input")
+	}
+	reader := bufio.NewReader(f)
+	return bufio.NewScanner(reader)
+}
+
+type targetArea struct {
+	startx int
+	endx   int
+	starty int
+	endy   int
+}
+
+func ParseInput(line string) targetArea {
+	target := targetArea{}
+	acc := ""
+	for i := 0; i < len(line); i++ {
+		switch line[i] {
+		case '1', '2', '3', '4', '5', '6', '7', '8', '9', '0', '-':
+			acc += string(line[i])
+		case '.':
+			i++ // skip the second .
+			if target.startx == 0 {
+				target.startx = mustAtoi(acc)
+			} else {
+				target.starty = mustAtoi(acc)
+			}
+			acc = ""
+		case ',':
+			target.endx = mustAtoi(acc)
+			acc = ""
+		default: // all other characters do nothing
+		}
+		target.endy = mustAtoi(acc)
+	}
+	return target
+}
+
+func InTarget(x, y int, target targetArea) bool {
+	return x >= target.startx && x <= target.endx && y <= target.endy && y >= target.starty
+}
+
+func BeyondTarget(x, y int, target targetArea) bool {
+	return x > target.endx || y < target.starty
+}
+
+type probe struct {
+	xvelocity int
+	yvelocity int
+	x         int
+	y         int
+	maxy      int
+}
+
+func (p *probe) Step() {
+	p.x += p.xvelocity
+	p.y += p.yvelocity
+	if p.xvelocity > 0 {
+		p.xvelocity--
+	} else if p.xvelocity < 0 {
+		p.xvelocity++
+	}
+	p.yvelocity--
+	if p.y > p.maxy {
+		p.maxy = p.y
+	}
+}
+
+func partOne() {
+	scanner := makeScanner(false)
+
+	// read line
+	scanner.Scan()
+	line := scanner.Text()
+	target := ParseInput(line)
+	highestArc := 0
+	for j := 1; j < 50; j++ {
+		for k := 1; k < 100; k++ {
+			initx := j
+			inity := k
+			p := &probe{
+				xvelocity: initx,
+				yvelocity: inity,
+			}
+			for {
+				p.Step()
+				if InTarget(p.x, p.y, target) {
+					if p.maxy > highestArc {
+						highestArc = p.maxy
+					}
+				}
+				if BeyondTarget(p.x, p.y, target) {
+					break
+				}
+			}
+		}
+	}
+	fmt.Println(highestArc)
+}
+
+func partTwo() {
+	scanner := makeScanner(false)
+
+	// read line
+	scanner.Scan()
+	line := scanner.Text()
+	target := ParseInput(line)
+	hits := 0
+	for j := 0; j < 1000; j++ {
+		for k := -200; k < 1000; k++ {
+			initx := j
+			inity := k
+			p := &probe{
+				xvelocity: initx,
+				yvelocity: inity,
+			}
+			for {
+				p.Step()
+				if InTarget(p.x, p.y, target) {
+					hits++
+					break
+				}
+				if BeyondTarget(p.x, p.y, target) {
+					break
+				}
+			}
+		}
+	}
+	fmt.Println(hits)
+}

17/main_test.go

@@ -0,0 +1,15 @@
+package main
+
+import "testing"
+
+func TestInTarget(t *testing.T) {
+	target := targetArea{
+		startx: 20,
+		endx:   30,
+		starty: -10,
+		endy:   -5,
+	}
+	if !InTarget(28, -7, target) {
+		t.Fail()
+	}
+}