Add 2023 Day 03 Part 1 solution

Author: palinkiewicz

adventofcode2023/Day03.kt

@@ -0,0 +1,74 @@
+package adventofcode2023
+
+import java.io.File
+
+object Day03 {
+    fun part1(inputs: List<String>) {
+        val firstDigitChecks = setOf(
+            Pair(-1, 0),
+            Pair(-1, -1),
+            Pair(0, -1),
+            Pair(-1, 1),
+            Pair(0, 1)
+        )
+        val centralDigitChecks = setOf(
+            Pair(0, 1),
+            Pair(0, -1)
+        )
+        val lastDigitChecks = setOf(
+            Pair(1, 0),
+            Pair(1, 1),
+            Pair(0, 1),
+            Pair(1, -1),
+            Pair(0, -1)
+        )
+
+        fun checkPositions(x: Int, y: Int, checks: Set<Pair<Int, Int>>): Boolean {
+            return checks.any {
+                val checkX = x + it.first
+                val checkY = y + it.second
+
+                if (checkX < 0 || checkY < 0
+                    || checkX >= inputs[0].length || checkY >= inputs.size
+                ) {
+                    false
+                } else {
+                    inputs[checkY][checkX] != '.'
+                }
+            }
+        }
+
+        fun checkPartNumberDigit(x: Int, y: Int): Boolean =
+            (x > 0 && !inputs[y][x - 1].isDigit() && checkPositions(x, y, firstDigitChecks)
+                    || x < inputs[0].length - 1 && !inputs[y][x + 1].isDigit() && checkPositions(x, y, lastDigitChecks)
+                    || checkPositions(x, y, centralDigitChecks))
+
+        var sum = 0
+
+        for (y in inputs.indices) {
+            var x = 0
+            while (x < inputs[0].length) {
+                if (inputs[y][x].isDigit()) {
+                    var isPartNumber = checkPartNumberDigit(x, y)
+                    var number = inputs[y][x].toString()
+
+                    while (x < inputs[0].length - 1 && inputs[y][x + 1].isDigit()) {
+                        x++
+                        number += inputs[y][x]
+                        if (!isPartNumber && checkPartNumberDigit(x, y)) isPartNumber = true
+                    }
+
+                    if (isPartNumber) sum += number.toInt()
+                }
+                x++
+            }
+        }
+
+        println(sum)
+    }
+}
+
+fun main() {
+    val inputs = File("resources/adventofcode2023/Day03.txt").readLines()
+    Day03.part1(inputs)
+}