Day 14

14/01.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+
+rules=()
+n_step=10
+read polymer
+read
+
+while read line; do
+  rules+=( ${line% ->*}'|'${line#*-> } )
+done
+
+for ((i=0; i<$n_step; i++)); do
+  polymer_size=0
+  while [ $polymer_size -lt ${#polymer} ]; do
+    polymer_size=${#polymer}
+    for rule in ${rules[@]}; do
+      polymer=${polymer//${rule:0:2}/${rule:0:1}'|'${rule:3:1}'|'${rule:1:1}}
+    done
+  done
+  polymer=${polymer//'|'/}
+done
+
+occurences=( $(printf "%s\n" $(sed 's/\(.\)/\1 /g' <<< $polymer) | sort | uniq -c \
+                   | sort -nr | sed 's/.$//') )
+echo $((occurences[0]-occurences[-1]))