Merge pull request #5 from palinkiewicz/2023_d04

palinkiewicz · web-flow · commit 3e80f7e73e4e · 2023-12-04T19:18:35.000+01:00
2023 Day 04
diff --git a/README.md b/README.md
@@ -5,8 +5,9 @@ In this repository, I am going to store my solutions to the [Advent of Code](htt
 I started taking part in the event in 2023 but may also consider doing tasks from the previous years.
 
 ## 2023
-| | My solution | My inputs |
-| --- | --- | --- |
-| [Day 1: Trebuchet?!](https://adventofcode.com/2023/day/1) | [Solution](/adventofcode2023/Day01.kt) | [Inputs](/resources/adventofcode2023/Day01.txt) |
+|                                                              | My solution                            | My inputs                                       |
+|--------------------------------------------------------------|----------------------------------------|-------------------------------------------------|
+| [Day 1: Trebuchet?!](https://adventofcode.com/2023/day/1)    | [Solution](/adventofcode2023/Day01.kt) | [Inputs](/resources/adventofcode2023/Day01.txt) |
 | [Day 2: Cube Conundrum](https://adventofcode.com/2023/day/2) | [Solution](/adventofcode2023/Day02.kt) | [Inputs](/resources/adventofcode2023/Day02.txt) |
-| [Day 3: Gear Ratios](https://adventofcode.com/2023/day/3) | [Solution](/adventofcode2023/Day03.kt) | [Inputs](/resources/adventofcode2023/Day03.txt) |
+| [Day 3: Gear Ratios](https://adventofcode.com/2023/day/3)    | [Solution](/adventofcode2023/Day03.kt) | [Inputs](/resources/adventofcode2023/Day03.txt) |
+| [Day 4: Scratchcards](https://adventofcode.com/2023/day/4)   | [Solution](/adventofcode2023/Day04.kt) | [Inputs](/resources/adventofcode2023/Day04.txt) |
diff --git a/adventofcode2023/Day04.kt b/adventofcode2023/Day04.kt
@@ -0,0 +1,39 @@
+package adventofcode2023
+
+import java.io.File
+import kotlin.math.pow
+
+object Day04 {
+    private fun countCorrectNumbersOnCard(line: String): Int {
+        val numbers = line.split(": ")[1].split(" | ")
+        val winningNumbers = numbers[0].split(" ").filter { it != "" }
+        val actualNumbers = numbers[1].split(" ").filter { it != "" }
+        return actualNumbers.count { winningNumbers.contains(it) }
+    }
+
+    fun part1(inputs: List<String>) {
+        println(inputs.sumOf { line ->
+            val correctNumbersCount = countCorrectNumbersOnCard(line)
+            if (correctNumbersCount == 0) 0 else 2.0.pow(correctNumbersCount - 1).toInt()
+        })
+    }
+
+    fun part2(inputs: List<String>) {
+        val scratchcardsCounters = IntArray(inputs.size) { 1 }
+
+        for (i in inputs.indices) {
+            val correctNumbersCount = countCorrectNumbersOnCard(inputs[i])
+            for (j in i + 1..i + correctNumbersCount) {
+                scratchcardsCounters[j] += scratchcardsCounters[i]
+            }
+        }
+
+        println(scratchcardsCounters.sum())
+    }
+}
+
+fun main() {
+    val inputs = File("resources/adventofcode2023/Day04.txt").readLines()
+    Day04.part1(inputs)
+    Day04.part2(inputs)
+}
diff --git a/resources/adventofcode2023/Day04.txt b/resources/adventofcode2023/Day04.txt
