Day 10

10/part1.js

@@ -0,0 +1,87 @@
+const { readFileSync } = require("fs");
+// Parse Input
+const inputFile = "input.txt";
+const input = readFileSync(inputFile).toString();
+const grid = [];
+input
+  .trim()
+  .split("\n")
+  .forEach((line) => grid.push(line.split("")));
+
+let trailheads = [];
+
+for (let y = 0; y < grid.length; y++) {
+  const line = grid[y];
+  for (let x = 0; x < line.length; x++) {
+    const element = line[x];
+    if (element == "0") {
+      trailheads.push({
+        id: trailheads.length,
+        start: [x, y],
+      });
+    }
+  }
+}
+
+const directions = [
+  [0, -1],
+  [-1, 0],
+  [1, 0],
+  [0, 1],
+];
+
+function isInGrid(coord) {
+  let x = coord[0];
+  let y = coord[1];
+  return !(x < 0 || y < 0 || x >= grid[0].length || y >= grid.length);
+}
+
+function computeTrailhead(th) {
+  const path = [
+    {
+      thId: th.id,
+      currentValue: 0,
+      coord: th.start,
+    },
+  ];
+
+  let endCoords = [];
+
+  while (path.length > 0) {
+    let currentPath = path.pop();
+    let currentValue = currentPath.currentValue;
+    let coord = currentPath.coord;
+
+    directions.forEach((d) => {
+      let checkedCoord = [coord[0] + d[0], coord[1] + d[1]];
+      if (
+        isInGrid(checkedCoord) &&
+        currentValue == 8 &&
+        grid[checkedCoord[1]][checkedCoord[0]] == 9 &&
+        endCoords.find(
+          (ec) => ec[0] == checkedCoord[0] && ec[1] == checkedCoord[1]
+        ) == null
+      ) {
+        endCoords.push(checkedCoord);
+      } else if (
+        isInGrid(checkedCoord) &&
+        grid[checkedCoord[1]][checkedCoord[0]] == currentValue + 1
+      ) {
+        path.push({
+          thId: th.id,
+          currentValue: currentValue + 1,
+          coord: checkedCoord,
+        });
+      }
+    });
+  }
+
+  return endCoords.length;
+}
+
+let result = 0;
+trailheads.forEach((th) => {
+  result += computeTrailhead(th);
+});
+
+console.log(result);

10/part2.js

@@ -0,0 +1,84 @@
+const { readFileSync } = require("fs");
+// Parse Input
+const inputFile = "input.txt";
+const input = readFileSync(inputFile).toString();
+const grid = [];
+input
+  .trim()
+  .split("\n")
+  .forEach((line) => grid.push(line.split("")));
+
+let trailheads = [];
+
+for (let y = 0; y < grid.length; y++) {
+  const line = grid[y];
+  for (let x = 0; x < line.length; x++) {
+    const element = line[x];
+    if (element == "0") {
+      trailheads.push({
+        id: trailheads.length,
+        start: [x, y],
+      });
+    }
+  }
+}
+
+const directions = [
+  [0, -1],
+  [-1, 0],
+  [1, 0],
+  [0, 1],
+];
+
+function isInGrid(coord) {
+  let x = coord[0];
+  let y = coord[1];
+  return !(x < 0 || y < 0 || x >= grid[0].length || y >= grid.length);
+}
+
+function computeTrailhead(th) {
+  const path = [
+    {
+      thId: th.id,
+      currentValue: 0,
+      coord: th.start,
+    },
+  ];
+
+  let endCoords = [];
+
+  while (path.length > 0) {
+    let currentPath = path.pop();
+    let currentValue = currentPath.currentValue;
+    let coord = currentPath.coord;
+
+    directions.forEach((d) => {
+      let checkedCoord = [coord[0] + d[0], coord[1] + d[1]];
+      if (
+        isInGrid(checkedCoord) &&
+        currentValue == 8 &&
+        grid[checkedCoord[1]][checkedCoord[0]] == 9
+      ) {
+        endCoords.push(checkedCoord);
+      } else if (
+        isInGrid(checkedCoord) &&
+        grid[checkedCoord[1]][checkedCoord[0]] == currentValue + 1
+      ) {
+        path.push({
+          thId: th.id,
+          currentValue: currentValue + 1,
+          coord: checkedCoord,
+        });
+      }
+    });
+  }
+
+  return endCoords.length;
+}
+
+let result = 0;
+trailheads.forEach((th) => {
+  result += computeTrailhead(th);
+});
+
+console.log(result);