Shellcheck fixes and minor cleanup

Avoid sed when tr can do the job
Ignore folders for previous years

Author: einarjon

.gitignore

@@ -1 +1,2 @@
-*.txt*
+./*.txt*
+201*/

02.sh

@@ -4,5 +4,5 @@ IFS=$'-:\ \n'
 while read -r m M b c; do x=${c//[^$b]}; (( ${#x} >= m && ${#x} <= M && ++ans)); done < "${1:-2.txt}"
 echo "2A: $ans"
 ans=0
-while read m M b c; do x=${c:m-1:1}; y=${c:M-1:1}; [[ $x != $y ]] && [[ $b == $x || $b == $y ]] && ((++ans)); done < ${1:-2.txt}
+while read -r m M b c; do x=${c:m-1:1}; y=${c:M-1:1}; [[ $x != "$y" ]] && [[ $b == "$x" || $b == "$y" ]] && ((++ans)); done < "${1:-2.txt}"
 echo "2B: $ans"

06.sh

@@ -1,7 +1,6 @@
 #! /usr/bin/env bash
 X=abcdefghijklmnopqrstuvwxyz; x=$X; a=0
-A=($(sed s/^$/X/ "${1:-6.txt}"))
-A+=(X)
+A=($(sed s/^$/X/ "${1:-6.txt}") X)
 while read -r -n1 i; do
     [ "$i" = X ] && { ((a+=26-${#x})); x=$X; }
     x=${x/$i}

11.sh

@@ -18,7 +18,7 @@ while [ ${#I} != 0 ]; do
         C[i]=.$l.; l=
     done
     B=("${C[@]}")
-    I=${!CHANGE[@]}
+    I=${!CHANGE[*]}
     ((++round==1)) && B=("${C[@]//X/x}")
     #((round%10)) || echo "$round: ${#CHANGE[@]}"
 done
@@ -30,9 +30,9 @@ B=(L${A//?/L}L); for i in "${A[@]}"; do B+=(L${i}L); done; B+=($B)
 J=$(seq ${#A}); I=$(seq ${#A[@]}); change=1; round=0
 while [ ${#change} != 0 ]; do
     change=""; C=($B); l=""
-    for i in $I; do # shellcheck disable=SC2034
+    for i in $I; do
         for j in $J; do
-            x=${B[i]:j:1}
+            x=${B[i]:$j:1}
             [[ "$x" != "L" && "$x" != "X" ]] && l+=$x && continue
             r=${B[i]:j+1}; r=${r//.}; R=${B[i]:0:j}; R=${R//.}
             s=${R: -1}${r:0:1}

13.sh

@@ -1,7 +1,7 @@
 #! /usr/bin/env bash
 IFS=$',\n'
 input=${1:-13.txt}
-A=($(sed s/x,//g "$input"))
+A=($(tr -ds 'x' ',' < "$input"))
 time=$A; min=($A 0)
 for i in "${A[@]:1}"; do
     w=$((i-time%i))

21.sh

@@ -3,7 +3,7 @@ IFS=$' \n' input=${1:-21.txt}
 A=($(grep -o "contains.*" "$input" | grep -o "[a-z]*" | grep -v contains| sort | uniq -c))
 i=0;
 while read -r a b; do
-   C[i++]=$(grep -w "$b" "$input" | grep -o ".*(" | grep -o "[a-z]*" | sort | uniq -c | grep -w "$a" | sed "s/[0-9 ]*//" | tr '\n' ' ')
+   C[i++]=$(grep -w "$b" "$input" | grep -o ".*(" | grep -o "[a-z]*" | sort | uniq -c | grep -w "$a" | tr -ds '0-9\n' ' ')
 done < <(printf "%s %s\n" "${A[@]}")
 
 space="^[[:space:]]+$"