Day 1 Part 2

1/2/puzzle.txt

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+--- Part Two ---
+
+Your calculation isn't quite right. It looks like some of the
+digits are actually spelled out with letters: one, two, three, four, five, six,
+seven, eight, and nine also count as valid "digits".
+
+Equipped with this new information, you now need to find the real first and last
+digit on each line. For example:
+
+two1nine
+eightwothree
+abcone2threexyz
+xtwone3four
+4nineeightseven2
+zoneight234
+7pqrstsixteen
+
+In this example, the calibration values are 29, 83, 13, 24, 42, 14, and 76.
+Adding these together produces 281.
+
+What is the sum of all of the calibration values?

1/2/solution.sh

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+#!/usr/bin/env bash
+
+set -o errexit
+set -o nounset
+set -o pipefail
+if [[ "${TRACE-0}" == "1" ]]; then
+  set -o xtrace
+fi
+
+cd "$(dirname "$0")"
+
+main ()
+{
+  numbers="[[:digit:]]|one|two|three|four|five|six|seven|eight|nine"
+  numbers_reverse="[[:digit:]]|eno|owt|eerht|ruof|evif|xis|neves|thgie|enin"
+  declare -A digits=([one]=1 [two]=2 [three]=3 [four]=4 [five]=5 [six]=6 [seven]=7 [eight]=8 [nine]=9)
+  declare -a components
+  declare -i result=0
+  while read -r line; do
+    first=$(grep -E -o "${numbers}" <<< "${line}" | head -n 1)
+    last=$(rev <<< "${line}" | grep -E -o "${numbers_reverse}" | rev | head -n 1)
+    first=$([[ ! ${first} =~ ^[0-9]$ ]] && echo "${digits[${first}]}" || echo "${first}")
+    last=$([[ ! ${last} =~ ^[0-9]$ ]] && echo "${digits[${last}]}" || echo "${last}")
+    components+=("${first}${last}")
+  done < input.txt
+  for value in "${components[@]}"; do
+    (( result += value ))
+  done
+  echo "${result}"
+}
+
+main