Finish day 17

2 files changed, 72 insertions, 8 deletions

diff --git a/README.md b/README.md
index a6cb346..a055eac 100644
--- a/README.md
+++ b/README.md
@@ -1,11 +1,14 @@
 # Advent of Code 2021 in Kotlin
+
 ![Kotlin](https://img.shields.io/badge/Kotlin-grey?logo=Kotlin)
-![](https://img.shields.io/badge/⭐%20stars-34-yellow)
-![](https://img.shields.io/badge/📅%20days-17-blue)
+![](https://img.shields.io/badge/⭐%20stars-36-yellow)
+![](https://img.shields.io/badge/📅%20days-18-blue)
 
-Welcome to the Advent of Code[^aoc] Kotlin project created by [tchojnacki][github] using the [Advent of Code Kotlin Template][template] delivered by JetBrains.
+Welcome to the Advent of Code[^aoc] Kotlin project created by [tchojnacki][github] using
+the [Advent of Code Kotlin Template][template] delivered by JetBrains. See other solutions [here][awesome].
 
 ## Progress
+
 | Day                             | Part 1 | Part 2 |
 |---------------------------------|:------:|:------:|
 | Day 1: Sonar Sweep              |   🌟   |   🌟   |
@@ -24,7 +27,7 @@ Welcome to the Advent of Code[^aoc] Kotlin project created by [tchojnacki][githu
 | Day 14: Extended Polymerization |   🌟   |   🌟   |
 | Day 15: Chiton                  |   🌟   |   🌟   |
 | Day 16: Packet Decoder          |   🌟   |   🌟   |
-| Day 17: Trick Shot              |        |        |
+| Day 17: Trick Shot              |   🌟   |   🌟   |
 | Day 18: Snailfish               |   🌟   |   🌟   |
 | Day 19: Beacon Scanner          |        |        |
 | Day 20: Trench Map              |        |        |
@@ -34,12 +37,16 @@ Welcome to the Advent of Code[^aoc] Kotlin project created by [tchojnacki][githu
 | Day 24: Arithmetic Logic Unit   |        |        |
 | Day 25: Sea Cucumber            |        |        |
 
-
 [^aoc]:
-    [Advent of Code][aoc] – An annual event of Christmas-oriented programming challenges started December 2015.
-    Every year since then, beginning on the first day of December, a programming puzzle is published every day for twenty-four days.
-    You can solve the puzzle and provide an answer using the language of your choice.
+[Advent of Code][aoc] – An annual event of Christmas-oriented programming challenges started December 2015.
+Every year since then, beginning on the first day of December, a programming puzzle is published every day for
+twenty-four days.
+You can solve the puzzle and provide an answer using the language of your choice.
 
 [aoc]: https://adventofcode.com
+
 [github]: https://github.com/tchojnacki
+
 [template]: https://github.com/kotlin-hands-on/advent-of-code-kotlin-template
+
+[awesome]: https://github.com/Bogdanp/awesome-advent-of-code
diff --git a/src/Day17.kt b/src/Day17.kt
index 32f47fe..5eaf498 100644
--- a/src/Day17.kt
+++ b/src/Day17.kt
@@ -1,3 +1,60 @@
+import kotlin.math.max
+import kotlin.math.sign
+
+data class Target(val left: Int, val right: Int, val bottom: Int, val top: Int)
+
+class Probe(private var vel: Pos2D, private val target: Target) {
+    companion object {
+        fun search(target: Target): Pair<Int, Int> {
+            var highest = 0
+            var count = 0
+
+            for (vx in 0..1000) {
+                for (vy in -1000..1000) {
+                    val probe = Probe(Pos2D(vx, vy), target)
+                    var currentHighest = 0
+
+                    while (probe.canHitTarget) {
+                        probe.step()
+                        currentHighest = max(currentHighest, probe.pos.y)
+
+                        if (probe.isInTarget) {
+                            count++
+                            highest = max(highest, currentHighest)
+                            break
+                        }
+                    }
+                }
+            }
+
+            return highest to count
+        }
+    }
+
+    private var pos = Pos2D(0, 0)
+
+    fun step() {
+        pos += vel
+        vel = vel.copy(x = vel.x - vel.x.sign, y = vel.y - 1)
+    }
+
+    val canHitTarget
+        get() = pos.y > target.bottom
+
+    val isInTarget
+        get() = pos.x in target.left..target.right && pos.y in target.bottom..target.top
+}
+
 fun main() {
+    fun bothParts(input: Target): Pair<Int, Int> = Probe.search(input)
+
+    val testInput = Target(20, 30, -10, -5)
+    val testOutput = bothParts(testInput)
+    check(testOutput.first == 45)
+    check(testOutput.second == 112)
 
+    val input = Target(192, 251, -89, -59)
+    val output = bothParts(input)
+    println(output.first)
+    println(output.second)
 }