2022 - Day 8

2022-12-19 13:53:33 +01:00
parent 86256daae8
commit 0a35f702fb
5 changed files with 301 additions and 0 deletions
--- a/2022/08/PART1.md
+++ b/2022/08/PART1.md
@@ -0,0 +1,33 @@
+--- Day 8: Treetop Tree House ---
+
+The expedition comes across a peculiar patch of tall trees all planted carefully in a grid. The Elves explain that a previous expedition planted these trees as a reforestation effort. Now, they're curious if this would be a good location for a tree house.
+
+First, determine whether there is enough tree cover here to keep a tree house hidden. To do this, you need to count the number of trees that are visible from outside the grid when looking directly along a row or column.
+
+The Elves have already launched a quadcopter to generate a map with the height of each tree (your puzzle input). For example:
+
+```
+30373
+25512
+65332
+33549
+35390
+```
+
+Each tree is represented as a single digit whose value is its height, where 0 is the shortest and 9 is the tallest.
+
+A tree is visible if all of the other trees between it and an edge of the grid are shorter than it. Only consider trees in the same row or column; that is, only look up, down, left, or right from any given tree.
+
+All of the trees around the edge of the grid are visible - since they are already on the edge, there are no trees to block the view. In this example, that only leaves the interior nine trees to consider:
+
+- The top-left 5 is visible from the left and top. (It isn't visible from the right or bottom since other trees of height 5 are in the way.)
+- The top-middle 5 is visible from the top and right.
+- The top-right 1 is not visible from any direction; for it to be visible, there would need to only be trees of height 0 between it and an edge.
+- The left-middle 5 is visible, but only from the right.
+- The center 3 is not visible from any direction; for it to be visible, there would need to be only trees of at most height 2 between it and an edge.
+- The right-middle 3 is visible from the right.
+- In the bottom row, the middle 5 is visible, but the 3 and 4 are not.
+
+With 16 trees visible on the edge and another 5 visible in the interior, a total of 21 trees are visible in this arrangement.
+
+Consider your map; how many trees are visible from outside the grid?
--- a/2022/08/PART2.md
+++ b/2022/08/PART2.md
@@ -0,0 +1,35 @@
+--- Part Two ---
+
+Content with the amount of tree cover available, the Elves just need to know the best spot to build their tree house: they would like to be able to see a lot of trees.
+
+To measure the viewing distance from a given tree, look up, down, left, and right from that tree; stop if you reach an edge or at the first tree that is the same height or taller than the tree under consideration. (If a tree is right on the edge, at least one of its viewing distances will be zero.)
+
+The Elves don't care about distant trees taller than those found by the rules above; the proposed tree house has large eaves to keep it dry, so they wouldn't be able to see higher than the tree house anyway.
+
+In the example above, consider the middle 5 in the second row:
+
+30373
+25512
+65332
+33549
+35390
+Looking up, its view is not blocked; it can see 1 tree (of height 3).
+Looking left, its view is blocked immediately; it can see only 1 tree (of height 5, right next to it).
+Looking right, its view is not blocked; it can see 2 trees.
+Looking down, its view is blocked eventually; it can see 2 trees (one of height 3, then the tree of height 5 that blocks its view).
+A tree's scenic score is found by multiplying together its viewing distance in each of the four directions. For this tree, this is 4 (found by multiplying 1 _ 1 _ 2 \* 2).
+
+However, you can do even better: consider the tree of height 5 in the middle of the fourth row:
+
+30373
+25512
+65332
+33549
+35390
+Looking up, its view is blocked at 2 trees (by another tree with a height of 5).
+Looking left, its view is not blocked; it can see 2 trees.
+Looking down, its view is also not blocked; it can see 1 tree.
+Looking right, its view is blocked at 2 trees (by a massive tree of height 9).
+This tree's scenic score is 8 (2 _ 2 _ 1 \* 2); this is the ideal spot for the tree house.
+
+Consider each tree on your map. What is the highest scenic score possible for any tree?
--- a/2022/08/input.txt
+++ b/2022/08/input.txt
@@ -0,0 +1,99 @@
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--- a/2022/08/sample.txt
+++ b/2022/08/sample.txt
@@ -0,0 +1,5 @@
+30373
+25512
+65332
+33549
+35390
--- a/2022/08/solution.ts
+++ b/2022/08/solution.ts
@@ -0,0 +1,129 @@
+const sample = await Deno.readTextFile("sample.txt");
+const input = await Deno.readTextFile("input.txt");
+
+/**** PART 1 ********************************/
+
+const solvePart1 = (data: string): number => {
+  const grid = data
+    .split("\n")
+    .filter(Boolean)
+    .map((line) => line.split("").filter(Boolean).map(parseFloat));
+
+  let counter = 0;
+
+  for (let y = 0; y < grid.length; y += 1) {
+    for (let x = 0; x < grid[0].length; x += 1) {
+      const height = grid[y][x];
+      let visibleUntil = true;
+      let visibleFrom = true;
+
+      /* Detect view on Y */
+      let verticalView = true;
+      for (let y1 = 0; y1 < grid.length; y1 += 1) {
+        if (y1 < y) {
+          visibleUntil = visibleUntil && grid[y1][x] < height;
+        }
+        if (y1 > y) {
+          visibleFrom = visibleFrom && grid[y1][x] < height;
+        }
+      }
+      verticalView = verticalView && (visibleUntil || visibleFrom);
+
+      /* Detect view on X */
+      let horizontalView = true;
+      visibleUntil = true;
+      visibleFrom = true;
+      for (let x1 = 0; x1 < grid.length; x1 += 1) {
+        if (x1 < x) {
+          visibleUntil = visibleUntil && grid[y][x1] < height;
+        }
+        if (x1 > x) {
+          visibleFrom = visibleFrom && grid[y][x1] < height;
+        }
+      }
+      horizontalView = horizontalView && (visibleUntil || visibleFrom);
+      if (horizontalView || verticalView) {
+        counter = counter + 1;
+      }
+    }
+  }
+  return counter;
+};
+
+console.log("Sample:", solvePart1(sample)); // 21
+console.log("Input", solvePart1(input)); // 1851
+
+/**** PART 2 ********************************/
+
+const solvePart2 = (data: string): number => {
+  const grid = data
+    .split("\n")
+    .filter(Boolean)
+    .map((line) => line.split("").filter(Boolean).map(parseFloat));
+
+  let highestCounter = 0;
+  for (let y = 0; y < grid.length; y += 1) {
+    const row = grid[y];
+    for (let x = 0; x < row.length; x += 1) {
+      let counter = 1;
+      const height = row[x];
+
+      let yCounter = 0;
+      for (let y2 = y + 1; y2 < grid.length; y2 += 1) {
+        const treeHeight = grid[y2][x];
+        if (treeHeight === undefined) {
+          break;
+        }
+        yCounter += 1;
+        if (treeHeight >= height) {
+          break;
+        }
+      }
+      counter = yCounter;
+      yCounter = 0;
+      for (let y2 = y - 1; y2 >= 0; y2 -= 1) {
+        const treeHeight = grid[y2][x];
+        if (treeHeight === undefined) {
+          break;
+        }
+        yCounter += 1;
+        if (treeHeight >= height) {
+          break;
+        }
+      }
+      counter *= yCounter;
+      let xCounter = 0;
+      for (let x2 = x + 1; x2 < row.length; x2 += 1) {
+        const treeHeight = grid[y][x2];
+        if (treeHeight === undefined) {
+          break;
+        }
+        xCounter += 1;
+        if (treeHeight >= height) {
+          break;
+        }
+      }
+      counter *= xCounter;
+      xCounter = 0;
+      for (let x2 = x - 1; x2 >= 0; x2 -= 1) {
+        const treeHeight = grid[y][x2];
+        if (treeHeight === undefined) {
+          break;
+        }
+        xCounter += 1;
+        if (treeHeight >= height) {
+          break;
+        }
+      }
+      counter *= xCounter;
+      if (counter > highestCounter) {
+        highestCounter = counter;
+      }
+    }
+  }
+
+  return highestCounter;
+};
+
+console.log("Sample:", solvePart2(sample)); // 8
+console.log("Input", solvePart2(input)); // 574080