AOC2019day16part1

16.sh

#!/bin/bash

set -eu

declare -ai input basepattern

read -r inputstr < "${1:?}"

for ((i=0; i < ${#inputstr}; i++)); do
  input+=("${inputstr:$i:1}")
done

basepattern=(0 1 0 -1)

declare -ai coeff

IFS="
"
coeffs=()
for ((i=0; i < ${#input[@]}; i++)); do
  for ((j=0; j < ${#input[@]}; j++)); do
    coeff[j]=${basepattern[((j+1) / (i+1)) % 4]}
  done
  coeffs+=("${coeff[*]}")
done

for phase in {1..100}; do
  results=()

  for ((i=0; i < ${#inputstr}; i++)); do
    ans=$(echo "${input[*]}" | paste -d \* - <(echo "${coeffs[i]}") | paste -sd+ | bc)
    results[i]=${ans: -1:1}
  done

  echo "After $phase phases: ${results[@]}"
  input=("${results[@]}")
done