day 7

app/src/main/kotlin/day07/Day07.kt

@@ -0,0 +1,63 @@
+package day07
+
+import kotlin.io.println
+import kotlin.collections.listOf
+import kotlin.coroutines.*
+
+class Day07 {
+    fun parse(input: String): List<Pair<Long, List<Long>>> {
+        return input.lines().map { line ->
+            val split = line.split(":")
+            Pair(split[0].toLong(), split[1].trim().split(" ").map { it.toLong() })
+        }
+    }
+
+    fun part1(input: String): Long {
+        return parse(input)
+            .filter { tryOperations(it, listOf("+", "*")) }
+            .map { it.first }
+            .sum()
+    }
+
+    fun tryOperations(equation: Pair<Long, List<Long>>, operations: List<String>): Boolean {
+        var operPermutations: List<List<String>> = listOf(listOf())
+        for (i in 0..<equation.second.count() - 1) {
+            operPermutations = getCombos(operPermutations, operations)
+        }
+        for (opers in operPermutations) {
+            var total = equation.second[0]
+            for (i in 1..<equation.second.count()) {
+                when (opers[i - 1]) {
+                   "+" -> total += equation.second[i]
+                   "*" -> total *= equation.second[i]
+                   "||" -> total = "${total}${equation.second[i]}".toLong()
+                }
+            }
+            if (total == equation.first) {
+                return true
+            }
+        }
+        return false
+    }
+
+    fun getCombos(combos: List<List<String>>, items: List<String>): List<List<String>> {
+        var newCombos: MutableList<List<String>> = mutableListOf()
+        for (combo in combos) {
+            for (item in items) {
+                newCombos.add(combo + item)
+            }
+        }
+        return newCombos
+    }
+
+    fun part2(input: String): Long {
+        return parse(input)
+            .filter {
+                tryOperations(it, listOf("+", "*", "||"))
+            }
+            .map { it.first }
+            .sum()
+    }
+}
+
+

app/src/test/kotlin/day07/Day07Test.kt

@@ -0,0 +1,41 @@
+package day07
+
+import kotlin.test.Test
+import util.InputDownloader
+
+class Day07Test {
+    val dayNum = 7
+    val day = Day07()
+
+    val input = InputDownloader().getInput(dayNum)
+    val example = InputDownloader().getExample(dayNum)
+
+    @Test fun part1Example() {
+        part1(example, 3749)
+    }
+
+    @Test fun part1Solution() {
+        part1(input, 1289579105366)
+    }
+
+    @Test fun part2Example() {
+        part2(example, 11387)
+    }
+
+    @Test fun part2Solution() {
+        part2(input, 92148721834692)
+    }
+
+    fun part1(input: String, expected: Long) {
+        val output = day.part1(input)
+        println("output: $output")
+        assert(output == expected)
+    }
+
+    fun part2(input: String, expected: Long) {
+        val output = day.part2(input)
+        println("output: $output")
+        assert(output == expected)
+    }
+}
+