advent-of-code/2024/day-16/solution-1.sh

#!/usr/bin/env bash

FUNCNEST=99999
FILE=test-input-1

# Load map
read -r -a MAP_ARRAY <<< "$( < "$FILE" paste -s -d "" | sed -E 's/(.)(.)/\1 \2 /g' )"
#read -r -a CHECKPOINT_ARRAY <<< "$( < "$FILE" paste -s -d "" | sed -E 's/(.)(.)/\1 \2 /g' )"
MAP_WIDTH=$(( $( head -1 "$FILE" | wc -c ) -1 ))
MAP_LEN=${#MAP_ARRAY[@]}
MAP_HEIGHT=$( < "$FILE" wc -l )
printf "Map len: %s Map width: %s Map height: %s\n" "$MAP_LEN" "$MAP_WIDTH" "$MAP_HEIGHT"
DIR_UP=$(( - MAP_WIDTH ))
DIR_DOWN=$MAP_WIDTH
DIR_LEFT=-1
DIR_RIGHT=1

print_map () {
  printf "%s " "${MAP_ARRAY[@]}" | fold -w $(( MAP_WIDTH * 2 ))
  printf "\n"
}

# Get starting position
for (( i=0; i<MAP_LEN; i++ ))
do
  if [[ ${MAP_ARRAY[$i]} == "S" ]]
  then
    START_POSITION=$i
    MAP_ARRAY[START_POSITION]="X"
    break
  fi
done
printf "Start position: %s\n" "$START_POSITION"

# Get end position
for (( i=0; i<MAP_LEN; i++ ))
do
  if [[ ${MAP_ARRAY[$i]} == "E" ]]
  then
    END_POSITION=$i
    MAP_ARRAY[END_POSITION]="X"
    break
  fi
done
printf "End position: %s\n" "$END_POSITION"

print_map

# Mark all checkpoints
declare -A CHECKPOINT_ARRAY
CHECKPOINT_ARRAY[$START_POSITION]=0
for (( i=0; i<MAP_LEN; i++ ))
do
  if [[ ${MAP_ARRAY[$i]} != "." ]] ;then continue ;fi
  STEP=$i
  ADJ_COUNT=0
  UP=$(( STEP + DIR_UP ))
  DOWN=$(( STEP + DIR_DOWN ))
  LEFT=$(( STEP + DIR_LEFT ))
  RIGHT=$(( STEP + DIR_RIGHT ))
  if [[ ${MAP_ARRAY[$UP]} == "." ]] && [[ $UP -gt 0 ]]
  then
    (( ADJ_COUNT++ ))
  fi
  if [[ ${MAP_ARRAY[$DOWN]} == "." ]] && [[ $DOWN -lt $MAP_LEN ]]
  then
    (( ADJ_COUNT++ ))
  fi
  if [[ ${MAP_ARRAY[$LEFT]} == "." ]]
  then
    (( ADJ_COUNT++ ))
  fi
  if [[ ${MAP_ARRAY[$RIGHT]} == "." ]]
  then
    (( ADJ_COUNT++ ))
  fi
  if [[ $ADJ_COUNT -gt 2 ]]
  then
    MAP_ARRAY[STEP]=X
    CHECKPOINT_ARRAY[$STEP]=0
  fi
done
CHECKPOINT_ARRAY[$END_POSITION]=0
printf "%s " "${!CHECKPOINT_ARRAY[@]}"
printf "\n"

# Iterate over checkpoints and print pairings
declare -A CHECKPOINT_PAIRS
declare -A CHECKPOINT_PAIR_WEIGHTS
get_weight_change () {
  local POSITION=$1
  local NEXT_POSITION=$2
  local DIRECTION=$3
  # For same directions, weight change is 1
  if [[ $(( NEXT_POSITION - POSITION )) -eq $DIR_UP ]] && [[ $(( DIRECTION % 2 )) -eq 0 ]]
  then
    printf "1"
    return 0
  elif [[ $(( NEXT_POSITION - POSITION )) -eq $DIR_DOWN ]] && [[ $(( DIRECTION % 3 )) -eq 0 ]]
  then
    printf "1"
    return 0
  elif [[ $(( NEXT_POSITION - POSITION )) -eq $DIR_LEFT ]] && [[ $(( DIRECTION % 5 )) -eq 0 ]]
  then
    printf "1"
    return 0
  elif [[ $(( NEXT_POSITION - POSITION )) -eq $DIR_RIGHT ]] && [[ $(( DIRECTION % 7 )) -eq 0 ]]
  then
    printf "1"
    return 0
  fi
  # For different directions, weight change is 1000
  printf "1000"
}
recurse_travel () {
  local POSITION=$1
  local CHECKPOINT=$2
  local DIRECTION=$3
  local WEIGHT=$4
  local UP=$(( POSITION - MAP_WIDTH ))
  local DOWN=$(( POSITION + MAP_WIDTH ))
  local LEFT=$(( POSITION - 1 ))
  local RIGHT=$(( POSITION + 1 ))
  # Search adjacent tiles
  # Recurse if it's movable
  # Add a checkpoint pair and weights if checkpoint found
  if [[ $(( DIRECTION % 2 )) -eq 0 ]] && [[ $UP -gt 0 ]]
  then
    if [[ ${MAP_ARRAY[$UP]} == "." ]]
    then
      WEIGHT_CHANGE=$( get_weight_change "$POSITION" "$UP" "$DIRECTION" )
      recurse_travel "$UP" "$CHECKPOINT" "$(( 2 * 5 * 7 ))" "$(( WEIGHT + WEIGHT_CHANGE ))"
    elif [[ -v CHECKPOINT_ARRAY[$UP] ]]
    then
      WEIGHT_CHANGE=$( get_weight_change "$POSITION" "$UP" "$DIRECTION" )
      CHECKPOINT_PAIRS[$UP]=$CHECKPOINT
      CHECKPOINT_PAIR_WEIGHTS["$UP-$CHECKPOINT"]=$(( WEIGHT + WEIGHT_CHANGE ))
    fi
  fi
  if [[ $(( DIRECTION % 3 )) -eq 0 ]] && [[ $DOWN -lt $MAP_LEN ]]
  then
    if [[ ${MAP_ARRAY[$DOWN]} == "." ]]
    then
      WEIGHT_CHANGE=$( get_weight_change "$POSITION" "$DOWN" "$DIRECTION" )
      recurse_travel "$DOWN" "$CHECKPOINT" "$(( 3 * 5 * 7 ))" "$(( WEIGHT + WEIGHT_CHANGE ))"
    elif [[ -v CHECKPOINT_ARRAY[$DOWN] ]]
    then
      WEIGHT_CHANGE=$( get_weight_change "$POSITION" "$DOWN" "$DIRECTION" )
      CHECKPOINT_PAIRS[$DOWN]=$CHECKPOINT
      CHECKPOINT_PAIR_WEIGHTS["$DOWN-$CHECKPOINT"]=$(( WEIGHT + WEIGHT_CHANGE ))
    fi
  fi
  if [[ $(( DIRECTION % 5 )) -eq 0 ]]
  then
    if [[ ${MAP_ARRAY[$LEFT]} == "." ]]
    then
      WEIGHT_CHANGE=$( get_weight_change "$POSITION" "$LEFT" "$DIRECTION" )
      recurse_travel "$LEFT" "$CHECKPOINT" "$(( 2 * 3 * 5 ))" "$(( WEIGHT + WEIGHT_CHANGE ))"
    elif [[ -v CHECKPOINT_ARRAY[$LEFT] ]]
    then
      WEIGHT_CHANGE=$( get_weight_change "$POSITION" "$LEFT" "$DIRECTION" )
      CHECKPOINT_PAIRS[$LEFT]=$CHECKPOINT
      CHECKPOINT_PAIR_WEIGHTS["$LEFT-$CHECKPOINT"]=$(( WEIGHT + WEIGHT_CHANGE ))
    fi
  fi
  if [[ $(( DIRECTION % 7 )) -eq 0 ]]
  then
    if [[ ${MAP_ARRAY[$RIGHT]} == "." ]]
    then
      WEIGHT_CHANGE=$( get_weight_change "$POSITION" "$RIGHT" "$DIRECTION" )
      recurse_travel "$RIGHT" "$CHECKPOINT" "$(( 2 * 3 * 7 ))" "$(( WEIGHT + WEIGHT_CHANGE ))"
    elif [[ -v CHECKPOINT_ARRAY[$RIGHT] ]]
    then
      WEIGHT_CHANGE=$( get_weight_change "$POSITION" "$RIGHT" "$DIRECTION" )
      CHECKPOINT_PAIRS[$RIGHT]=$CHECKPOINT
      CHECKPOINT_PAIR_WEIGHTS["$RIGHT-$CHECKPOINT"]=$(( WEIGHT + WEIGHT_CHANGE ))
    fi
  fi
}
for CHECKPOINT in "${!CHECKPOINT_ARRAY[@]}"
do
  recurse_travel "$CHECKPOINT" "$CHECKPOINT" "$CHECKPOINT" "$(( 2 * 3 * 5 * 7 ))" "0"
done
for CHECKPOINT in "${!CHECKPOINT_PAIRS[@]}"
do
  printf "DEST %s from checkpoint %s\n" "${CHECKPOINT_PAIRS[$CHECKPOINT]}" "$CHECKPOINT"
done
for CHECKPOINT in "${!CHECKPOINT_PAIR_WEIGHTS[@]}"
do
  printf "Weight %s for checkpoint pair %s\n" "${CHECKPOINT_PAIR_WEIGHTS[$CHECKPOINT]}" "$CHECKPOINT"
done

# Score the path
#

print_map