complete day 2, part 2

day2/part 2.sh

@@ -0,0 +1,55 @@
+#!/usr/bin/env bash
+test_report(){
+  # count numbers 1 through 3 in the list of differences
+  numerality=`echo ${report_diff[@]} \
+  | sed 's/-//g'| grep -w -o "[1-3]" | wc -l`
+
+  # test if each number is 1 through 3
+  if [ $numerality -eq $diff_length ]; then
+    # count minus signs
+    negativity=`echo ${report_diff[@]} \
+    | grep -o "-" | wc -l`
+    # we only want to see if all the signs are the same
+    if [ $negativity -eq 0 ] || [ $negativity -eq $diff_length ]; then
+      unset report_diff[@]
+      return 0
+    fi
+  fi
+  unset report_diff[@]
+  return 1
+}
+
+report_to_diff(){
+  declare -g -a report
+  # assign each number to an array element
+  report=( `echo $1` )
+  diff_length=$((${#report[@]}-1))
+  declare -g -a report_diff
+  # find differences between levels in report
+  for i in `seq 1 $diff_length`; do
+    report_diff+="`bc <<<${report[$i]}-${report[$i-1]}` "
+  done
+}
+
+problem_dampener(){
+  levels=$((`echo $REPLY | grep -o ' ' | wc -l`+1))
+  # try each report with a level removed, until we find one that's safe
+  for level in `seq 1 $levels`; do
+    dampened_report="`echo $REPLY | cut --complement -d ' ' -f $level`"
+    report_to_diff "$dampened_report"
+    if test_report; then
+      return 0
+    fi
+  done
+  return 1
+}
+
+while read; do
+  report_to_diff "$REPLY"
+  if test_report; then
+    (( safe++ ))
+  elif problem_dampener; then
+    (( safe++ ))
+  fi
+done < <(cat input)
+echo $safe