add 2023/day3 solution

Author: libhide

src/main/kotlin/advent2023/Day03.kt

@@ -0,0 +1,92 @@
+package advent2023
+
+import advent2023.shared.Point2D
+
+class Day03(private val input: List<String>) {
+
+    fun solvePart1(): Int {
+        val coordinates = mutableSetOf<Point2D>()
+        val grid = input.map { line -> line.map { char -> char } }
+
+        grid.forEachIndexed { rowIndex, line ->
+            line.forEachIndexed { colIndex, char ->
+                // If valid symbol
+                if (!char.isDigit() && char != '.') {
+                    // Check adjacent box for a digit
+                    ((rowIndex - 1)..(rowIndex + 1)).forEach { r ->
+                        ((colIndex - 1)..(colIndex + 1)).forEach { c ->
+                            // Boundary conditions
+                            if (r >= 0 && r < grid.size && c >= 0 && c < grid[r].size) {
+                                if (grid[r][c].isDigit()) {
+                                    // We have a number! Find the point of its first digit
+                                    var temp = c
+                                    while (temp > 0 && grid[r][temp - 1].isDigit()) {
+                                        temp -= 1
+                                    }
+                                    coordinates.add(Point2D(r, temp))
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+        val partNumbers = coordinates.map { coord -> coord.determineNumber(grid) }
+        return partNumbers.sum()
+    }
+
+    fun solvePart2(): Int {
+        val coordinates = mutableListOf<Pair<Point2D, Point2D>>()
+        val grid = input.map { line -> line.map { char -> char } }
+
+        grid.forEachIndexed { rowIndex, line ->
+            line.forEachIndexed { colIndex, char ->
+                // Condition for identifying a Gear
+                if (char == '*') {
+                    val gearSet = mutableSetOf<Point2D>()
+                    // Check adjacent box for a digit
+                    ((rowIndex - 1)..(rowIndex + 1)).forEach { r ->
+                        ((colIndex - 1)..(colIndex + 1)).forEach { c ->
+                            if (r >= 0 && r < grid.size && c >= 0 && c < grid[r].size) {
+                                if (grid[r][c].isDigit()) {
+                                    // We have a number! Find the point of its first digit
+                                    var temp = c
+                                    while (temp > 0 && grid[r][temp - 1].isDigit()) {
+                                        temp -= 1
+                                    }
+                                    gearSet.add(Point2D(r, temp))
+                                }
+                            }
+                        }
+                    }
+                    if (gearSet.size == 2) {
+                        coordinates.add(Pair(gearSet.first(), gearSet.last()))
+                    }
+                }
+            }
+        }
+        val partNumbers = coordinates.map { gearSet ->
+            val first = gearSet.first.determineNumber(grid)
+            val second = gearSet.second.determineNumber(grid)
+            first * second
+        }
+        return partNumbers.sum()
+    }
+
+    private fun Point2D.determineNumber(grid: List<List<Char>>): Int {
+        val stringBuilder = StringBuilder()
+        var temp = y
+        while (temp < grid[x].size && grid[x][temp].isDigit()) {
+            stringBuilder.append(grid[x][temp])
+            temp += 1
+        }
+        return stringBuilder.toString().toInt()
+    }
+}
+
+fun main() {
+    val input = Resources.resourceAsListOfString("advent2023/day03.txt")
+    val day03 = Day03(input = input)
+    println("Part 1 Solution: ${day03.solvePart1()}")
+    println("Part 2 Solution: ${day03.solvePart2()}")
+}

src/main/kotlin/advent2023/shared/Point2D.kt

@@ -0,0 +1,3 @@
+package advent2023.shared
+
+data class Point2D(val x: Int, val y: Int)