Solution 2017-01 (Inverse Captcha)

Author: rhaendel

src/main/kotlin/de/ronny_h/aoc/year2017/day01/InverseCaptcha.kt

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+package de.ronny_h.aoc.year2017.day01
+
+import de.ronny_h.aoc.AdventOfCode
+
+fun main() = InverseCaptcha().run(1343, 1274)
+
+class InverseCaptcha : AdventOfCode<Int>(2017, 1) {
+    override fun part1(input: List<String>): Int = sumOfSameNumbersInDistance(input.first(), 1)
+    override fun part2(input: List<String>): Int = sumOfSameNumbersInDistance(input.first(), input.first().length / 2)
+
+    private fun sumOfSameNumbersInDistance(sequence: String, distance: Int): Int {
+        var sum = 0
+        sequence.forEachIndexed { i, n ->
+            if (n == sequence[(i + distance) % sequence.length]) {
+                sum += "$n".toInt()
+            }
+        }
+        return sum
+    }
+}

src/test/kotlin/de/ronny_h/aoc/year2017/day01/InverseCaptchaTest.kt

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+package de.ronny_h.aoc.year2017.day01
+
+import io.kotest.core.spec.style.StringSpec
+import io.kotest.data.forAll
+import io.kotest.data.row
+import io.kotest.matchers.shouldBe
+
+class InverseCaptchaTest : StringSpec({
+
+    "part 1: all the examples given" {
+        forAll(
+            row("1122", 3),
+            row("1111", 4),
+            row("1234", 0),
+            row("91212129", 9),
+        ) { sequence, sum ->
+            InverseCaptcha().part1(listOf(sequence)) shouldBe sum
+        }
+    }
+
+    "part 2: all the examples given" {
+        forAll(
+            row("1212", 6),
+            row("1221", 0),
+            row("123425", 4),
+            row("123123", 12),
+            row("12131415", 4),
+        ) { sequence, sum ->
+            InverseCaptcha().part2(listOf(sequence)) shouldBe sum
+        }
+    }
+})