Day 3 solution

src/Day03.kt

@@ -0,0 +1,94 @@
+fun main() {
+
+    data class Part(val number: Int, val startIndex : Int, val endIndex : Int, val line: Int? = null)
+    data class Symbol(val symbol: Char, val x: Int, val y: Int)
+
+    fun getPartsFromLines(input: List<String>): List<Part> {
+
+        val regexp = "\\d+".toRegex()
+        return input.mapIndexed { index, s ->
+            regexp.findAll(s)
+                .toList()
+                .map { Part(it.value.toInt(), it.range.first, it.range.last, index) }
+        }.flatten()
+    }
+
+    fun part1(input: List<String>) : Int {
+
+        val symbols = input.map {
+                line -> line.indices.filter { line[it] != '.' && !line[it].isDigit() }
+        }
+
+        val symbols2 = symbols.mapIndexed { index, ints ->
+            ints.map { i -> Symbol(input[index][i], index, i) }
+        }.flatten()
+
+        val values = getPartsFromLines(input)
+        val finalParts = mutableListOf<Part>()
+
+        symbols2.forEach { symbol ->
+
+                val symbolXRange = symbol.x-1..symbol.x+1
+                val symbolYRange = symbol.y-1..symbol.y+1
+
+                for (part in values) {
+
+                    if (part.line in symbolXRange){
+                        if (part.startIndex in symbolYRange || part.endIndex in symbolYRange){
+                            finalParts.add(part)
+                        }
+                    }
+                }
+        }
+
+        return finalParts.toSet().sumBy { it.number }
+    }
+
+    fun part2(input: List<String>) : Int {
+
+        val symbols = input.map {
+                line -> line.indices.filter { line[it] != '.' && !line[it].isDigit() }
+        }
+
+        val symbols2 = symbols.mapIndexed { index, ints ->
+            ints.map { i -> Symbol(input[index][i], index, i) }
+        }.flatten()
+            .filter { it.symbol == '*' }
+
+        val values = getPartsFromLines(input)
+
+        var gearRatio = 0
+
+        symbols2.forEach { symbol ->
+
+            val symbolXRange = symbol.x-1..symbol.x+1
+            val symbolYRange = symbol.y-1..symbol.y+1
+
+            val gearparts = mutableListOf<Part>()
+            for (part in values) {
+
+                if (part.line in symbolXRange){
+                    if (part.startIndex in symbolYRange || part.endIndex in symbolYRange){
+                        gearparts.add(part)
+                    }
+                }
+            }
+
+            if (gearparts.size == 2){
+                gearRatio += gearparts[0].number * gearparts[1].number
+            }
+            gearparts.clear()
+        }
+        return gearRatio
+    }
+
+    val testInput = readInput("Day03_test")
+    check(part1(testInput) == 4361)
+
+    val input = readInput("Day03")
+    part1(input).println()
+
+    check(part2(testInput) == 467835)
+    part2(input).println()
+
+}