aoc2021-3b.sh

#!/opt/homebrew/bin/bash

INPFILE=day3.txt
cp $INPFILE oday3s1.txt
cp $INPFILE cday3s1.txt
echo -n '^' > opatfile
echo -n '^' > cpatfile
len="$(($(head -n1 $INPFILE | wc -c) - 1))"
for z in $(seq 1 $len) ; do
    owanted=$(cat oday3s${z}.txt | cut -c${z} | sort | uniq -c | sort -n | tail -n1 | awk '{print $2}')
    cwanted=$(cat cday3s${z}.txt | cut -c${z} | sort | uniq -c | sort -rn | tail -n1 | awk '{print $2}')
    echo -n "$owanted" >> opatfile
    echo -n "$cwanted" >> cpatfile
    egrep -f opatfile oday3s${z}.txt > oday3s$(($z + 1)).txt
    egrep -f cpatfile cday3s${z}.txt > cday3s$(($z + 1)).txt
done