Day 03

day03.groovy

@@ -0,0 +1,139 @@
+import groovy.transform.TupleConstructor;
+
+
+def input = new File("input/day03.txt").readLines();
+
+@TupleConstructor
+class PartNumber {
+    Schematic schematic;
+    int x;
+    int y;
+    int len;
+    int value;
+
+    boolean isValid() {
+        int x0 = Math.max(0, x - 1);
+        int x1 = Math.min(schematic.width - 1, x + len + 1);
+        int y0 = Math.max(0, y - 1);
+        int y1 = Math.min(schematic.height - 1, y + 1);
+        for (int j in y0..y1) {
+            for (int i in x0..x1) {
+                char c = schematic.get(i, j);
+                if (!c.isDigit() && c != '.') {
+                    return true;
+                }
+            }
+        }
+
+        return false;
+    }
+
+    boolean includes(int px, int py) {
+        int x0 = Math.max(0, x - 1);
+        int x1 = Math.min(schematic.width - 1, x + len + 1);
+        int y0 = Math.max(0, y - 1);
+        int y1 = Math.min(schematic.height - 1, y + 1);
+
+        return x0 <= px && px <= x1 && y0 <= py && py <= y1;
+    }
+
+    String toString() {
+        int x0 = Math.max(0, x - 1);
+        int x1 = Math.min(schematic.width - 1, x + len + 1);
+        int y0 = Math.max(0, y - 1);
+        int y1 = Math.min(schematic.height - 1, y + 1);
+
+        def result = "";
+        for (int j in y0..y1) {
+            for (int i in x0..x1) {
+                result += schematic.get(i, j);
+            }
+            result += "\n";
+        }
+        return result;
+    }
+}
+
+class Schematic {
+    private final char[] arr;
+    final int width;
+    final int height;
+
+    private def partNumbersCache;
+
+    Schematic(List<String> input) {
+        arr = input.join("").toCharArray();
+        width = input[0].size();
+        height = input.size();
+    }
+
+    def get(int x, int y) {
+        int pos = x + y * width;
+        return arr[pos];
+    }
+
+    def getPartNumbers() {
+        if (partNumbersCache != null) {
+            return partNumbersCache;
+        }
+
+        def result = [];
+
+        def numberIndices = arr.findIndexValues { it.isDigit() };
+
+        int pnStart = numberIndices[0];
+        int curr, next;
+        for (int i = 0; i < numberIndices.size(); i++) {
+            curr = numberIndices[i];
+            next = numberIndices[i + 1] ?: -1;
+            if (next - curr == 1) {
+                continue;
+            }
+
+            int pnX = pnStart % width;
+            int pnY = Math.floor(pnStart / width);
+            def pnEnd = curr;
+            def pnLength = pnEnd - pnStart;
+            result << new PartNumber(this, pnX, pnY, pnLength, arr[pnStart..pnEnd].join("").toInteger());
+
+            pnStart = next;
+        }
+
+        partNumbersCache = result;
+        return result;
+    }
+
+    def getGears() {
+        def gearIndices = arr.findIndexValues { it == '*' };
+        return gearIndices.collect { 
+            int gX = it % width;
+            int gY = Math.floor(it / width);
+            return getPartNumbers().findAll { pn -> 
+                return pn.includes(gX, gY);
+            };
+        }.findAll { pnc -> pnc.size() == 2 };
+    }
+
+    String toString() {
+        def result = "";
+        for (int y = 0; y < height; y++) {
+            for (int x = 0; x < width; x++) {
+                result += this.get(x, y);
+            }
+            result += "\n";
+        }
+        return result;
+    }
+}
+
+def schematic = new Schematic(input);
+
+def partNumberSum = schematic.getPartNumbers().inject(0) { acc, it ->
+    return it.isValid() ? acc + it.value : acc;
+};
+println(partNumberSum);
+
+def gearRatioSum = schematic.getGears().inject(0) { acc, it ->
+    return acc + (it[0].value * it[1].value);
+};
+println(gearRatioSum);