2021 Day 17 Complete

2021/day17/input

@@ -0,0 +1 @@
+target area: x=277..318, y=-92..-53

2021/day17/main.go

@@ -0,0 +1,62 @@
+package main
+
+import (
+	"fmt"
+
+	h "git.bullercodeworks.com/brian/adventofcode/helpers"
+)
+
+// Target Area
+var x1, y1, x2, y2 int
+
+func main() {
+	inp := h.StdinToString()
+	fmt.Sscanf(inp, "target area: x=%d..%d, y=%d..%d", &x1, &x2, &y1, &y2)
+
+	var maxy int
+	r := make(map[h.Coordinate]bool)
+	b := 500
+
+	for x := b * -1; x < b; x++ {
+		for y := b * -1; y < b; y++ {
+			v := h.Coordinate{X: x, Y: y}
+			if m, ok := testForHit(h.Coordinate{}, v); ok {
+				if m > maxy {
+					maxy = m
+				}
+				r[v] = true
+			}
+		}
+	}
+	fmt.Println("Maximum Peak:", maxy)
+	fmt.Println("Valid Velocities:", len(r))
+}
+
+func testForHit(pos h.Coordinate, vel h.Coordinate) (int, bool) {
+	var maxy int
+	for {
+		pos.X += vel.X
+		pos.Y += vel.Y
+		if pos.Y > maxy {
+			maxy = pos.Y
+		}
+		if pos.X >= x1 && pos.X <= x2 && pos.Y >= y1 && pos.Y <= y2 {
+			return maxy, true
+		}
+		if vel.X == 0 && vel.Y < y1 {
+			return maxy, false
+		}
+		if vel.X > 0 {
+			vel.X--
+		}
+		if vel.X < 0 {
+			vel.X++
+		}
+		vel.Y--
+	}
+}
+
+type xy struct {
+	x int
+	y int
+}

2021/day17/testinput

@@ -0,0 +1 @@
+target area: x=20..30, y=-10..-5

helpers/helpers.go

@@ -108,6 +108,16 @@ func OptArgNumber(i int, def string) string {
 	return def
 }
 
+// StdinToString reads from stdin and returns a string
+func StdinToString() string {
+	var input string
+	scanner := bufio.NewScanner(os.Stdin)
+	for scanner.Scan() {
+		input += scanner.Text()
+	}
+	return input
+}
+
 // StdinToIntSlice reads from stdin and returns it as an int slice
 func StdinToIntSlice() []int {
 	var ret []int
@@ -148,16 +158,6 @@ func Itoa(i int) string {
 	return strconv.Itoa(i)
 }
 
-// StdinToString reads from stdin and returns a string
-func StdinToString() string {
-	var input string
-	scanner := bufio.NewScanner(os.Stdin)
-	for scanner.Scan() {
-		input += scanner.Text()
-	}
-	return input
-}
-
 // FileToStringSlice takes a file and returns it as a slice of strings
 func FileToStringSlice(fn string) []string {
 	return strings.Split(string(FileToBytes(fn)), "\n")
@@ -358,16 +358,37 @@ func IsPrime(value int) bool {
 	return value > 1
 }
 
-func Min(v1, v2 int) int {
+func Min(v1, v2 int, vrest ...int) int {
+	min := v2
 	if v1 < v2 {
-		return v1
+		min = v1
 	}
-	return v2
+	for i := range vrest {
+		if vrest[i] < min {
+			min = vrest[i]
+		}
+	}
+	return min
 }
 
-func Max(v1, v2 int) int {
+func Max(v1, v2 int, vrest ...int) int {
+	max := v2
 	if v1 > v2 {
-		return v1
+		max = v1
 	}
-	return v2
+	for i := range vrest {
+		if vrest[i] > max {
+			max = vrest[i]
+		}
+	}
+	return max
+}
+
+// Sum adds up all of the numbers from l to h
+func Sum(l, h int) int {
+	var ret int
+	for i := Min(l, h); i <= Max(l, h); i++ {
+		ret = ret + i
+	}
+	return ret
 }