advent-of-code/2024/day-5/solution-2.sh

#!/usr/bin/env bash

{
  while read -r LINE
  do
    GREP_EXPR=$( printf "%s"  "$LINE" | tr ',' '|' )
    MATCH_COUNT=0
    # Loop through rules and find a breaking rule
    while read -r RULE
    do
      GREPC=$( printf "%s" "$LINE" | grep -c "$RULE" ) 
      if [[ $GREPC -ne 1 ]]
      then
        #printf "%s rule violated for %s \n" "$RULE" "$LINE"
        MATCH_COUNT=1
        break
      fi
    # Filter rules that only has included pages
    done <<< "$( < input-rules grep -E "($GREP_EXPR)\\|($GREP_EXPR)" | sed 's/|/,.*/')" 
  
    # Don't process for valid lines
    [[ $MATCH_COUNT -eq 0 ]] && continue
    printf "%s\n" "$LINE"
  
  done < input-updates
} | {
  while read -r LINE # Generate a hashmap and rebuild the entire line from rules
  do
    CACHED_LINE=$( printf "%s" "$LINE" | tr ',' '\n' )
    while [[ $( printf "%s" "$CACHED_LINE" | wc -c ) -gt 0 ]]
    do
      # Loop through rules and build all the KVs
      DAG_GREP_EXPR=$( printf "%s"  "$CACHED_LINE" | paste -s -d '|' )
      KV_ARRAY=( $( < input-rules grep -E "($DAG_GREP_EXPR)\\|($DAG_GREP_EXPR)" | tr '|' ' ' | paste -s -d ' ') )
      # Going through dependencies to find final key
      KEY=${KV_ARRAY[0]}
      while true
      do
        BREAK=0
        for (( i=0; i<${#KV_ARRAY[@]}; i+=2 )) # Check if key exists
        do
          if [[ ${KV_ARRAY[$i]} -eq $KEY ]]
          then
            KEY=${KV_ARRAY[$i+1]}
	    BREAK=1
	    break
          fi
        done
	if [[ $BREAK -eq 1 ]] ; then continue ; else break ; fi
      done
      printf "%s\n" "$KEY"
      CACHED_LINE=$( printf "%s" "$CACHED_LINE" | grep -v "$KEY" )
    done | tac | paste -s -d' '
  done 
} |
  tee final-output |
  awk '
  BEGIN{ total = 0 } 
  {
    if (NF % 2 == 1) {
      idx = int( NF / 2 ) + 1
    } else {
      idx = NF / 2
    }
    total += $idx
  } 
  END{ print total }'