Impossibly slow Day 5 Part 2

5/2/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")"
+
+INPUT_FILE="$1"
+
+get_seed_pairs ()
+{
+  IFS=" " read -r -a seeds <<< "$(grep seeds "${INPUT_FILE}" | cut -d ' ' -f 2-)"
+  seed_count="${#seeds[@]}"
+  pairs=$((seed_count/2))
+  for ((i=0; i<pairs; i++)); do
+    j=$((i*2))
+    k=$((i*2+1))
+    seed_pairs[${seeds[${j}]}]="${seeds[${k}]}"
+  done
+}
+
+gen_map ()
+{
+  # Generates files for given index of map in input file.
+  local paragraph map_name map_content
+  paragraph=$(($1+1)) # number of paragraph in input file
+  map_name=$(awk -v RS= "{if(NR == ${paragraph}) print}" "${INPUT_FILE}" | head -n 1 | cut -d ' ' -f 1)
+  map_content=$(awk -v RS= "{if(NR == ${paragraph}) print}" "${INPUT_FILE}"| tail -n +2)
+  echo "${map_content}" > "${map_name}.map"
+  maps+=("${map_name}.map")
+}
+
+map_seed ()
+{
+  # Usage: map_seed MAP_FILE SEED_NUMBER
+  # Prints the mapping of the seed number in the give map.
+  local map seed dest_start source_start length diff
+  map="$1"
+  seed="$2"
+  while read -r line; do
+    dest_start=$(cut -d ' ' -f 1 <<< "${line}")
+    source_start=$(cut -d ' ' -f 2 <<< "${line}")
+    length=$(cut -d ' ' -f 3 <<< "${line}")
+    if [[ ${seed} -ge ${source_start} && ${seed} -le $((source_start+length-1)) ]]; then
+      diff=$((seed-source_start))
+      echo -n $((dest_start+diff))
+      return
+    fi
+  done < "${map}"
+  echo -n "${seed}" # no mapping
+}
+
+main ()
+{
+  declare -A seed_pairs=()
+  declare -a maps=()
+  local map_count destination lowest length seed
+  get_seed_pairs
+  map_count=$(awk -v RS= 'END {print NR}' "${INPUT_FILE}")
+  map_count=$((map_count-1)) # one of the paragraphs in the file is seeds
+  for ((i=1; i<=map_count; i++)); do
+    gen_map "${i}"
+  done
+  lowest=''
+  for s in "${!seed_pairs[@]}"; do
+    length=${seed_pairs[${s}]}
+    echo "running from start ${s} length ${length}"
+    for ((z=0; z<length; z++)); do
+      y=$((s+z))
+      destination=''
+      for map in "${maps[@]}"; do
+        if [[ -z ${destination} ]]; then
+          destination=$(map_seed "${map}" "${y}")
+        else
+          destination=$(map_seed "${map}" "${destination}")
+        fi
+      done
+      if [[ -z ${lowest} ]]; then
+        lowest="${destination}"
+      elif [[ ${destination} -lt ${lowest} ]]; then
+        lowest="${destination}"
+      fi
+      echo "iteration ${z} seed ${y} destination ${destination}"
+    done
+    echo "interim lowest: ${lowest}"
+  done
+  echo "${lowest}"
+  rm -f ./*.map
+}
+
+main