Day 25

25/01.sh

@@ -0,0 +1,51 @@
+#!/bin/bash
+
+max_i=0
+max_j=0
+declare -A grid
+while read line; do
+  max_j=${#line}
+  for ((j=0;j<max_j;j++)); do
+    if [[ ${line:$j:1} == '.' ]]; then
+      grid[$max_i,$j]=0
+    elif [[ ${line:$j:1} == '>' ]]; then
+      grid[$max_i,$j]=1
+    elif [[ ${line:$j:1} == 'v' ]]; then
+      grid[$max_i,$j]=2
+    fi
+  done
+  max_i=$((max_i+1))
+done
+
+changes=1
+south=0
+steps=0
+while [ $changes -eq 1 ]; do
+  changes=$south
+  declare -A new_grid
+  for ((i=0;i<max_i;i++)); do
+    for ((j=0;j<max_j;j++)); do
+      if [ $south -eq 0 ] && [ ${grid[$i,$j]} -eq 1 ] && [ ${grid[$i,$(((j+1)%max_j))]} -eq 0 ]; then
+        new_grid[$i,$j]=0
+        new_grid[$i,$(((j+1)%max_j))]=1
+        changes=1
+      elif [ $south -eq 1 ] && [ ${grid[$i,$j]} -eq 2 ] && [ ${grid[$(((i+1)%max_i)),$j]} -eq 0 ]; then
+        new_grid[$i,$j]=0
+        new_grid[$(((i+1)%max_i)),$j]=2
+        changes=1
+      elif [ -z ${new_grid[$i,$j]} ]; then
+        new_grid[$i,$j]=${grid[$i,$j]}
+      fi
+    done
+  done
+  south=$((1-south))
+  for ((i=0;i<max_i;i++)); do
+    for ((j=0;j<max_j;j++)); do
+      grid[$i,$j]=${new_grid[$i,$j]}
+    done
+  done
+  unset new_grid
+  steps=$((steps+south))
+done
+
+echo $steps