Day 22 Part 1

Author: albertobastos

input/d22.txt

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+depth: 10689
+target: 11,722

input/d22ex.txt

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+depth: 510
+target: 10,10

src/d22.js

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+console.time("d22");
+const rl = require("./utils").getInputRL("d22");
+
+let DEPTH;
+let TARGET; // {x, y}
+
+let erosion_levels = {}; // `x,y`: erosionLevel
+
+const ROCKY = 0;
+const WET = 1;
+const NARROW = 2;
+
+function programReadLine(rl) {
+ const depthRegex = /depth: (\d+)/;
+ const depthTarget = /target: (\d+),(\d+)/;
+ rl.on("line", line => {
+ let depthMatch = depthRegex.exec(line);
+ let targetMatch = depthTarget.exec(line);
+ if (depthMatch) {
+ DEPTH = Number(depthMatch[1]);
+ } else if (targetMatch) {
+ TARGET = {
+ x: Number(targetMatch[1]),
+ y: Number(targetMatch[2])
+ };
+ }
+ });
+
+ rl.on("close", () => {
+ console.log(DEPTH);
+ console.log(TARGET);
+ console.log("Answer (Part 1):", runPart1());
+ console.log("Answer (Part 2):");
+ console.timeEnd("d22");
+ });
+}
+
+function runPart1() {
+ let sum = 0;
+ for (let x = 0; x <= TARGET.x; x++) {
+ for (let y = 0; y <= TARGET.y; y++) {
+ sum += getErosionLevel(x, y) % 3;
+ }
+ }
+ return sum;
+}
+
+function getErosionLevel(x, y) {
+ let xy = `${x},${y}`;
+ let level = erosion_levels[xy];
+ if (level === undefined) {
+ level = (getGeologicIndex(x, y) + DEPTH) % 20183;
+ erosion_levels[xy] = level;
+ }
+ return level;
+}
+
+function getGeologicIndex(x, y) {
+ if (x === 0 && y === 0) {
+ return 0;
+ }
+ if (x === TARGET.x && y === TARGET.y) {
+ return 0;
+ }
+ if (x === 0 || y === 0) {
+ return x * 16807 + y * 48271;
+ }
+ return getErosionLevel(x - 1, y) * getErosionLevel(x, y - 1);
+}
+
+programReadLine(rl);