advent-of-code/2024/day-14/solution-2.sh

#!/usr/bin/env/bash

FILE=input
MAP_WIDTH=101
MAP_HEIGHT=103
MEDIAN_WIDTH=$(( MAP_WIDTH / 2 - 1 ))
if [[ $(( MAP_WIDTH % 2 )) -eq 1 ]]
then
  (( MEDIAN_WIDTH++ ))
fi
MEDIAN_HEIGHT=$(( MAP_HEIGHT / 2 - 1 ))
if [[ $(( MAP_HEIGHT % 2 )) -eq 1 ]]
then
  (( MEDIAN_HEIGHT++ ))
fi
printf "Median width: %s, median height: %s\n" "$MEDIAN_WIDTH" "$MEDIAN_HEIGHT"

# Load bot positions and velocities
read -r -a BOT_ARRAY <<< "$( grep -Eo '[-0-9]*' "$FILE" | paste -s -d " " )"
#printf "%s " "${BOT_ARRAY[@]}"
#printf "\n"
printf "Bot array size: %s\n" "${#BOT_ARRAY[@]}"

# Load arrangements for every second
#for SECONDS in $( seq 1 9999 )
for SECONDS in $( seq 6514 6516 )
do
  # Compute positions for each bot
  printf "Working on +%s seconds.\n" "$SECONDS"
  IFS=';'; read -r -a FINAL_ARRAY <<< "$(
    for (( i=0; i<${#BOT_ARRAY[@]}; i+=4 )) 
    do
      PX=${BOT_ARRAY[i]}
      PY=${BOT_ARRAY[i+1]}
      VX=${BOT_ARRAY[i+2]}
      VY=${BOT_ARRAY[i+3]}
      FINAL_X=$(( PX + ( VX * SECONDS ) ))
      FINAL_Y=$(( PY + ( VY * SECONDS ) ))
      printf "%s %s;" "$FINAL_X" "$FINAL_Y"
    done <<< "${BOT_ARRAY[@]}"
  )"
  unset IFS

  # Generate "empty" map
  # Map is a 1d array
  MAP_LEN=$(( MAP_HEIGHT * MAP_WIDTH ))
  read -r -a MAP_ARRAY <<< "$( 
    for (( i=0; i<MAP_LEN; i++ ))
    do
      printf ". "
    done
  )"

  # Calculate and map bot positions on the map
  while read -r RAW_X RAW_Y
  do
  
    # Adjust positions to be on map
    PX=$(( RAW_X % MAP_WIDTH ))
    if [[ $PX -lt 0 ]]
    then
      PX=$(( MAP_WIDTH + PX ))
    fi
    PY=$(( RAW_Y % MAP_HEIGHT ))
    if [[ $PY -lt 0 ]]
    then
      PY=$(( MAP_HEIGHT + PY ))
    fi

    # Calculate serial position and mark it
    POSITION=$(( PX + (PY -1)*MAP_WIDTH ))
    MAP_ARRAY[POSITION]=X
  
  done <<< "$( printf "%s\n" "${FINAL_ARRAY[@]}" )"

  # Print out map for manual review
  #printf "%s" "${MAP_ARRAY[@]}" | fold -w $(( MAP_WIDTH )) | grep -o 'XXXXXXXXXX' && break
  printf "%s" "${MAP_ARRAY[@]}" | fold -w $(( MAP_WIDTH ))
  printf "\n"

  printf "Final array length: %s, map array length: %s\n" "${#FINAL_ARRAY[@]}" "${#MAP_ARRAY[@]}"
  printf "\n"

  # Reset for next run
  unset MAP_ARRAY
  unset FINAL_ARRAY
done