Day 13

13/01.sh

@@ -0,0 +1,44 @@
+#!/bin/bash
+
+declare -A dots
+folds=()
+
+while read line; do
+  if [[ $line == *','* ]]; then
+    dots[$line]=1
+  else
+    folds+=( $(sed 's/fold along //' <<< $line) )
+  fi
+done
+
+fold=${folds[0]}
+fold_axis=$(sed 's/=.*$//' <<< $fold)
+fold_coord=$(sed 's/^.*=//' <<< $fold)
+new_dots=()
+todel_dots=()
+
+for dot in ${!dots[@]}; do
+  dot_x=$(sed 's/,.*$//' <<< $dot)
+  dot_y=$(sed 's/^.*,//' <<< $dot)
+  if [[ $fold_axis == 'x' ]]; then
+    if [ $dot_x -gt $fold_coord ]; then
+      new_dots+=( "$((fold_coord*2-dot_x)),$dot_y" )
+      todel_dots+=( $dot )
+    fi
+  else
+    if [ $dot_y -gt $fold_coord ]; then
+      new_dots+=( "$dot_x,$((fold_coord*2-dot_y))" )
+      todel_dots+=( $dot )
+    fi
+  fi
+done
+
+for todel_dot in ${todel_dots[@]}; do
+  unset dots[$todel_dot]
+done
+
+for new_dot in ${new_dots[@]}; do
+  dots[$new_dot]=1
+done
+
+echo ${#dots[@]}