Maya Herrscher
2 years ago
4 changed files with 240 additions and 0 deletions
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--- Day 8: Treetop Tree House --- |
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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. |
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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. |
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The Elves have already launched a quadcopter to generate a map with the height of each tree (your puzzle input). For example: |
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30373 |
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25512 |
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65332 |
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33549 |
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35390 |
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Each tree is represented as a single digit whose value is its height, where 0 is the shortest and 9 is the tallest. |
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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. |
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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: |
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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.) |
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The top-middle 5 is visible from the top and right. |
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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. |
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The left-middle 5 is visible, but only from the right. |
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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. |
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The right-middle 3 is visible from the right. |
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In the bottom row, the middle 5 is visible, but the 3 and 4 are not. |
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With 16 trees visible on the edge and another 5 visible in the interior, a total of 21 trees are visible in this arrangement. |
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Consider your map; how many trees are visible from outside the grid? |
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Your puzzle answer was 1823. |
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--- Part Two --- |
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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. |
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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.) |
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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. |
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In the example above, consider the middle 5 in the second row: |
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30373 |
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25512 |
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65332 |
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33549 |
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35390 |
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Looking up, its view is not blocked; it can see 1 tree (of height 3). |
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Looking left, its view is blocked immediately; it can see only 1 tree (of height 5, right next to it). |
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Looking right, its view is not blocked; it can see 2 trees. |
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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). |
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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). |
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However, you can do even better: consider the tree of height 5 in the middle of the fourth row: |
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30373 |
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25512 |
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65332 |
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33549 |
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35390 |
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Looking up, its view is blocked at 2 trees (by another tree with a height of 5). |
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Looking left, its view is not blocked; it can see 2 trees. |
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Looking down, its view is also not blocked; it can see 1 tree. |
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Looking right, its view is blocked at 2 trees (by a massive tree of height 9). |
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This tree's scenic score is 8 (2 * 2 * 1 * 2); this is the ideal spot for the tree house. |
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Consider each tree on your map. What is the highest scenic score possible for any tree? |
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Your puzzle answer was 211680. |
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Both parts of this puzzle are complete! They provide two gold stars: ** |
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@ -0,0 +1,60 @@ |
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#!/usr/bin/env python3 |
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import sys |
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def visible(t,x,y): |
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if x == 0 or y == 0 or x == (len(t[0]) - 1) or y == (len(t) - 1): |
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return 1 |
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h = t[y][x] |
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v = 1 |
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for r in [(0,x),(x+1,len(t[y]))]: # left, right |
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for i in range(*r): |
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if h <= t[y][i]: v = 0 |
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if v == 1: return v |
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else: v = 1 |
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for r in [(0,y),(y+1,len(t))]: # up, down |
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for i in range(*r): |
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if h <= t[i][x]: v = 0 |
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if v == 1: return v |
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else: v = 1 |
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return 0 |
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def scenic(t,x,y): |
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if x == 0 or y == 0 or x == (len(t[0]) - 1) or y == (len(t) - 1): |
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return 0 |
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h = t[y][x] |
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score = 1 |
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cur = 0 |
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for r in [(x-1,-1,-1),(x+1,len(t[y]))]: # left, right |
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for i in range(*r): |
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cur = cur + 1 |
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if h <= t[y][i]: break |
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score = score * cur |
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cur = 0 |
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for r in [(y-1,-1,-1),(y+1,len(t))]: # up, down |
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for i in range(*r): |
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cur = cur + 1 |
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if h <= t[i][x]: break |
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score = score * cur |
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cur = 0 |
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return score |
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if __name__ == '__main__': |
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trees = [[int(l) for l in list(line.strip('\n'))] for line in open(sys.argv[1])] |
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vis = 0 |
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scene = 0 |
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for i in range(len(trees)): |
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for j in range(len(trees[i])): |
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vis = vis + visible(trees,j,i) |
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sc_score = scenic(trees,j,i) |
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if sc_score > scene: scene = sc_score |
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# challenge 1 |
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res1 = str(vis) |
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print("challenge 1:" + "\n" + res1 + "\n") |
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# challenge 2 |
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res2 = str(scene) |
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print("challenge 2:" + "\n" + res2 + "\n") |
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@ -0,0 +1,5 @@ |
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30373 |
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25512 |
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65332 |
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33549 |
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35390 |
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020104234232554141451622326322264263647735447654367457344444465643453634336365231214525124433022444 |
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204201130004331123325262634265424363534754356365344543544653337444375665555552553542414222233041401 |
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231313304412112545143543446626577766674444573674633355336777737535543536546633462414421512204234400 |
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033341420245341341444352655236656744666536473763766674637573737455777566262423256254341313453322144 |
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440314332142235331442343546273646373345664657448647878767773563537357677642454354424141113554434301 |
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334433112533124466362636446457755674575647767878689757997654655557447467734646643623663324241123341 |
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222110343401032043553425111312244654332653464666435423342453322663424243153233322113032023202020223 |
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323230200411432130355525221321433355242633433225442453325522522622364253311533334354031100222010013 |
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310222312143433114242431355515315554643534324342445656666436353223444231435453241400213321330130010 |
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333003032313304033243534455111112214234262552344526635435332246231323535122413441024143242102302110 |
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113023202303413323324054115321135342223354425566256536556255312115424353351151533010221413210330113 |
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201002101132013010411214525353534241113423251253436544643553152152432455455322331331310031222312310 |
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010000023323114442204233214145222453523254543111213112525444545451354241122320331344023330301010000 |
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020221201301204043241340212025231451554512545355544454355334235544331435121232034423404333303220120 |
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211200133121002321411044312343241534545415435535214551522523534521342510432012433211020132222223110 |
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001010111333021232114033432123014243143421131445211232544521554534542030434313341020033312233321020 |
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110102200233103010320200140144034422131352541143533213514525422131220112004103004000011012120121220 |
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