advent-of-code/2024/day-17/solution-2.sh

#!/usr/bin/env bash

FILE=$1
ITER=1
MACHINE_ITER=999
DEBUG=false
INCREMENT=100000000000
TAIL_NUM=3

# Load registry values
REG_A=$(grep 'Register A:' "$FILE" | cut -f2 -d: )
REG_B=$(grep 'Register B:' "$FILE" | cut -f2 -d: )
REG_C=$(grep 'Register C:' "$FILE" | cut -f2 -d: )

# Rewrite registry A starting value
REG_A=100000000000000
#REG_A=164541160582800

# Load input string
read -r -a INPUT <<< "$(grep 'Program:' "$FILE" | cut -f2 -d: | tr ',' ' ' )"
INPUT_LEN=${#INPUT[@]}
printf "Registers A: %s B: %s C: %s\n" "$REG_A" "$REG_B" "$REG_C" >&2
#printf "Input: " >&2
#printf "%s " "${INPUT[@]}" >&2
#printf "\n" >&2

# Load machine operations
. machine.sh

# Iterate registry A until last nth digits are matched
PIN_DIGITS=0
while ! check_tail "$INPUT_LEN" "$PIN_DIGITS"
do
  while ! check_tail "$TAIL_NUM" "$PIN_DIGITS"
  do
    read -r -a OUTPUT <<< "$( execute_machine )"
    printf "Register A: %s\n" "$REG_A"
    printf "Output:\t"
    printf "%s " "${OUTPUT[@]}"
    printf "\n"
    printf "Input:\t"
    printf "%s " "${INPUT[@]}"
    printf "\n"
    (( REG_A+=INCREMENT))
    #(( ITER-- ))
    if [[ $ITER -eq 0 ]] ; then break ; fi
  done
  PIN_DIGITS=$TAIL_NUM
  printf "Matched digit. Reducing count"
  (( TAIL_NUM+=1 ))
  (( INCREMENT/= 50 ))
done