2022 day 8: Bash parts 1 & 2
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@@ -53,4 +53,70 @@ 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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To begin, [[file:8/input][get your puzzle input]].
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Your puzzle answer was =1698=.
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** --- Part Two ---
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Content with the amount of tree cover available, the Elves just need to
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know the best spot to build their tree house: they would like to be able
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to see a lot of /trees/.
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To measure the viewing distance from a given tree, look up, down, left,
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and right from that tree; stop if you reach an edge or at the first tree
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that is the same height or taller than the tree under consideration. (If
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a tree is right on the edge, at least one of its viewing distances will
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be zero.)
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The Elves don't care about distant trees taller than those found by the
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rules above; the proposed tree house has large
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[[https://en.wikipedia.org/wiki/Eaves][eaves]] to keep it dry, so they
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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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#+begin_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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#+end_example
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- Looking up, its view is not blocked; it can see =1= tree (of height
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=3=).
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- Looking left, its view is blocked immediately; it can see only =1=
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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
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(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
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distance in each of the four directions. For this tree, this is =4=
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(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
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middle of the fourth row:
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#+begin_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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#+end_example
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- Looking up, its view is blocked at =2= trees (by another tree with a
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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
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height =9=).
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This tree's scenic score is =8= (=2 * 2 * 1 * 2=); this is the ideal
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spot for the tree house.
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Consider each tree on your map. /What is the highest scenic score
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possible for any tree?/
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Your puzzle answer was =672280=.
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Both parts of this puzzle are complete! They provide two gold stars: **
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211
2022/day08/aoc.bash
Executable file
211
2022/day08/aoc.bash
Executable file
@@ -0,0 +1,211 @@
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#!/usr/bin/env bash
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#
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# aoc.bash: Advent of Code 2022, day 8
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#
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# Copyright (C) 2022 Bruno Raoult ("br")
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# Licensed under the GNU General Public License v3.0 or later.
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# Some rights reserved. See COPYING.
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#
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# You should have received a copy of the GNU General Public License along with this
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# program. If not, see <https://www.gnu.org/licenses/gpl-3.0-standalone.html>.
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#
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# SPDX-License-Identifier: GPL-3.0-or-later <https://spdx.org/licenses/GPL-3.0-or-later.html>
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. common.bash
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declare -a trees=() # trees height
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declare -Ai visible=() # visible if set
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declare -i size
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parse() {
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readarray -t trees
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size=${#trees[@]}
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}
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# y=${trees[0]:i:1}
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# xrev=${trees[i]:size-1:1}
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# yrev=${trees[size-1]:i:1}
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# printf "x=%d\n" "$x"
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# printf "y=%d\n" "$y"
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# printf "xrev=%d\n" "$xrev"
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# printf "yrev=%d\n" "$yrev"
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# height - return height of a tree
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# $1: reference of return value
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# $2, $3: x, y
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# x is column, y is row
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height() {
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local -n _ret="$1"
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local -i _x="$2" _y="$3"
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_ret=${trees[_y]:_x:1}
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}
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check_visible() {
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local -n _max="$1"
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local -i _x="$2" _y="$3" _c
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echo "m=$_max x=$x y=$y"
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height _c "$x" "y"
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printf "(%d,%d)=%d\n" "$x" "$y" "$_c"
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if (( _c > _max )); then
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printf "right visible (%d,%d)=%d\n" "$x" "$y" "$_c"
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(( visible[$x-$y]++, _max=_c ))
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(( _max == 9 )) && return 1
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fi
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return 0
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}
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part1() {
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declare -ig res
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local -i x y max c
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# left to right
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for ((y = 1; y < size -1; ++y)); do # row
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height max 0 "$y"
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printf "**** left=%d max=%d\n" "$i" "$max"
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(( max == 9 )) && continue
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for ((x = 1; x < size -1; ++x)); do # column
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check_visible max "$x" "$y" || break
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done
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done
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echo
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# right to left
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for ((y = 1; y < size -1; ++y)); do # row
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height max $((size - 1)) "$y"
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printf "**** right=%d max=%d\n" "$i" "$max"
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(( max == 9 )) && continue
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for ((x = size - 2; x > 0; --x)); do # column
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check_visible max "$x" "$y" || break
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done
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done
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echo
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# top to bottom
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for ((x = 1; x < size -1; ++x)); do # column
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height max "$x" 0
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printf "**** top=%d max=%d\n" "$i" "$max"
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(( max == 9 )) && continue
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for ((y = 1; y < size -1; ++y)); do # column
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check_visible max "$x" "$y" || break
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done
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done
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echo
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# bottom to top
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for ((x = 1; x < size -1; ++x)); do # row
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height max "$x" $((size - 1))
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printf "**** bottom=%d max=%d\n" "$i" "$max"
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(( max == 9 )) && continue
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for ((y = size - 2; y > 0; --y)); do # column
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check_visible max "$x" "$y" || break
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done
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done
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(( res = ${#visible[@]} + size * 4 - 4 ))
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}
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check_tree() {
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local -n res=$1
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local -i X="$2" Y="$3" c x y h
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local -ai vis=()
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height h "$X" "$Y"
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printf "********** part2(%d,%d) h=%d\n" "$X" "$Y" "$h"
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# east
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for ((x = X + 1; x < size ; ++x)); do
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height c "$x" "Y"
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printf "(%d,%d)=%d " "$x" "$Y" "$c"
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(( vis[0]++ ))
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((c >= h)) && break
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done
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(( res *= vis[0] ))
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echo
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printf "east=%d\n" "${vis[0]}"
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# west
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for ((x = X - 1; x >= 0; --x)); do
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height c "$x" "Y"
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printf "(%d,%d)=%d " "$x" "$Y" "$c"
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(( vis[1]++ ))
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((c >= h)) && break
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done
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(( res *= vis[1] ))
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echo
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printf "west=%d\n" "${vis[1]}"
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# south
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for ((y = Y + 1; y < size; ++y)); do
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height c "$X" "$y"
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printf "(%d,%d)=%d " "$X" "$y" "$c"
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(( vis[2]++ ))
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((c >= h)) && break
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done
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(( res *= vis[2] ))
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echo
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printf "south=%d\n" "${vis[2]}"
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# north
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for ((y = Y - 1; y >= 0; --y)); do
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height c "$X" "$y"
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printf "(%d,%d)=%d " "$X" "$y" "$c"
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(( vis[3]++ ))
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((c >= h)) && break
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done
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(( res *= vis[3] ))
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echo
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printf "north=%d\n" "${vis[3]}"
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# shellcheck disable=1102
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res=$(( "${vis[@]/%/ *}" 1))
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printf "res(%d,%d)=%d * %d * %d * %d = %d\n" "$X" "$Y" "${vis[0]}" "${vis[1]}" "${vis[2]}" "${vis[3]}" "$res"
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echo
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}
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part2() {
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local -ig res=0
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local -i tmp=1 x y
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for ((x = 1; x < size - 1; ++x)); do
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for ((y = 1; y < size - 1; ++y)); do
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#echo "ZOB $x $y"
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check_tree tmp "$x" "$y"
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if ((tmp > res)); then
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((res = tmp))
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printf "NEW MAX at (%d,%d)=%d\n" "$x" "$y" "$tmp"
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fi
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done
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done
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#check_tree tmp 2 3
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}
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solve() {
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if ((part == 1)); then
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part1
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else
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part2
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fi
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}
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main "$@"
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exit 0
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for k in "${!visible[@]}"; do
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printf "k=%s %d\n" "$k" "${visible[$k]}"
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done
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echo
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for (( i = 1; i < size - 1; ++i )); do
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max=${trees[i]:size-1:1}
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printf "i=%d max=%d\n" "$i" "$max"
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for (( j = size - 2; j > 0; --j )); do
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if (( ${trees[i]:j:1} > max)); then
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printf "(%d,%d)=%d max=%d\n" "$i" "$j" "${trees[i]:j:1}" "$max"
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(( visible[$i-$j]++ ))
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max=${trees[i]:j:1}
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printf "new max=%d\n" "$max"
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(( max == 9 )) && break
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fi
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done
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done
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echo
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for k in "${!visible[@]}"; do
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printf "k=%s %d\n" "$k" "${visible[$k]}"
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done
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res=${#visible[@]}
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