2020: Cleanup and deuglify

Use globs when possible, and avoid pipes/subshells.

3, 9 and 16 had small errors that could result in the
wrong answer for part 2.

19 speeded up 15x by using named variables instead of subshells.
No subshells, shorter regex, and cache hits are 6x better.

Author: einarjon

01.sh

@@ -1,7 +1,9 @@
 #! /usr/bin/env bash
-input=${1:-1.txt}
-A=($(sort -n "$input"));
-for a in "${A[@]}"; do grep -q -- ^$((2020-a))$ "$input" && break; done
-echo "1A: $((2020-a)) + $a = $(((2020-a)*a))"
-b=:; for a in "${A[@]}";do for i in "${A[@]}"; do grep -q -- ^$((2020-a-i))$ "$input" && b=break; $b; done; $b; done
-echo "1B: $((2020-a-i)) + $a + $i = $(((2020-a-i)*a*i))"
+A=($(sort -n "${1:-1.txt}"))
+for i in "${A[@]}"; do B[i]=1; done
+for a in "${A[@]}"; do ((b=2020-a, B[b] > 0)) && break; done
+echo "1A: $b + $a = $((b*a))"
+for i in "${!A[@]}";do for b in "${A[@]:i+1}"; do
+    ((a=A[i], c=2020-a-b, c > 0 && B[c] > 0)) && break 2;
+done; done
+echo "1B: $c + $a + $b = $((c*a*b))"

02.sh

@@ -1,8 +1,10 @@
 #! /usr/bin/env bash
-ans=0
-IFS=$'-:\ \n'
-while read -r m M b c; do x=${c//[^$b]}; (( ${#x} >= m && ${#x} <= M && ++ans)); done < "${1:-2.txt}"
+ans=0 ans2=0
+IFS=$' -:\n'
+while read -r m M b c; do
+    x=${c//[^$b]}; y=${c:m-1:1}; z=${c:M-1:1};
+    (( ${#x} >= m && ${#x} <= M && ++ans ))
+    [[ $y != "$z" ]] && [[ $b == "$y" || $b == "$z" ]] && ((++ans2))
+done < "${1:-2.txt}"
 echo "2A: $ans"
-ans=0
-while read -r m M b c; do x=${c:m-1:1}; y=${c:M-1:1}; [[ $x != "$y" ]] && [[ $b == "$x" || $b == "$y" ]] && ((++ans)); done < "${1:-2.txt}"
-echo "2B: $ans"
+echo "2B: $ans2"

03.sh

@@ -1,8 +1,7 @@
 #! /usr/bin/env bash
-A=($(< "${1:-3.txt}")); l=${#A[0]}; k=0; j=3; total=1; x=""
-for i in "${A[@]}"; do x+=${i:k:1}; ((k=(k+j)%l)); done; x=${x//\.}
-echo "3A: ${#x}"
-idx2=$(seq 0 2 $((${#A[@]}-1)))
-for j in 1 3 5 7; do x=""; k=0; for i in "${A[@]}"; do x+=${i:k:1}; ((k=(k+j)%l)); done; x=${x//\.}; total+="*${#x}"; done
-x=""; k=0; for i in $idx2; do x+=${A[i]:k:1}; ((k=(k+2)%l)); done ; x=${x//\.}; total+="*${#x}"
-echo "3B: ${total:2} = $((total))"
+A=($(< "${1:-3.txt}")); l=${#A[0]}; N=${#A[@]}; k=0; j=3; x=""
+for i in "${A[@]}"; do x+=${i:k:1}; ((k=(k+j)%l)); done; x=${x//\.}; total=${#x}
+echo "3A: $total"
+for j in 1 5 7; do x=""; k=0; for i in "${A[@]}"; do x+=${i:k:1}; ((k=(k+j)%l)); done; x=${x//\.}; total+="*${#x}"; done
+x=""; k=0; for ((i=0;i<N;i+=2)); do x+=${A[i]:k:1}; ((k=(k+1)%l)); done ; x=${x//\.}; total+="*${#x}"
+echo "3B: ${total} = $((total))"

08.sh

@@ -20,8 +20,8 @@ solve8 || echo "8A: $acc"
 
 A=("${B[@]}");
 for k in "${!A[@]}"; do
-    if   [ ${A[k]:0:3} = nop ]; then A[k]=${A[k]/nop/jmp};
-    elif [ ${A[k]:0:3} = jmp ]; then A[k]=${A[k]/jmp/nop};
+    if   [[ ${A[k]} = nop* ]]; then A[k]=jmp${A[k]:3};
+    elif [[ ${A[k]} = jmp* ]]; then A[k]=nop${A[k]:3};
     else continue; fi
     solve8 && break
     A=("${B[@]}")

09.sh

@@ -2,23 +2,22 @@
 A=($(< "${1:-9.txt}"))
 idx=(${!A[@]})
 for i in "${idx[@]:25}"; do
-    b=:
     for j in "${idx[@]:i-25:25-1}"; do
-        [[ ${A[j]} -ge ${A[i]} ]] && continue
+        ((A[j] >= A[i])) && continue
         for k in "${idx[@]:j+1:i-j-1}"; do
-            ((A[j]+A[k] == A[i])) && b=break; $b
+            ((A[j]+A[k] == A[i])) && break 2
         done
-        $b
     done
-    [ "$b" = ":" ] && echo "9A: line $i = ${A[i]}" && break
+    ((A[j]+A[k] != A[i])) && break
 done
+echo "9A: line $i = ${A[i]}"
 
 k=0; j=0; sum=${A[j++]}
 while [ "$sum" != "${A[i]}" ]; do
-    if   [[ $sum -lt ${A[i]} ]]; then ((sum+=A[j++]))
-    elif [[ $sum -gt ${A[i]} ]]; then ((sum-=A[k++]))
+    if   ((sum < A[i])); then ((sum+=A[j++]))
+    elif ((sum > A[i])); then ((sum-=A[k++]))
     fi
-    [[ $j -ge $i ]] && echo NOT FOUND && break
+    ((j >= i)) && echo NOT FOUND && break
 done
-B=($(printf "%s\n" "${A[*]:k:j-k}" | sort -n))
+B=($(printf "%s\n" "${A[@]:k:j-k}" | sort -n))
 echo "9B: $k..$j = $((B[0]+B[-1]))"

14.sh

@@ -12,12 +12,11 @@ printf -v sum "+%s" "${mem[@]}"
 echo "14A: $((sum))"
 
 r() {
-    local x=${2/X/0}
-    if [ "$x" = "$2" ]; then
-        mem2[$1|(2#$x)]=$3
-    else
-        r "$1" "$x" "$3"
+    if [[ $2 == *X* ]]; then
+        r "$1" "${2/X/0}" "$3"
         r "$1" "${2/X/1}" "$3"
+    else
+        mem2[$1|(2#$2)]=$3
     fi
 }
 

16.sh

@@ -6,7 +6,7 @@ A=($(grep "," "$input"))
 sum=""
 for i in "${!A[@]}"; do
   for j in ${A[i]//,/ }; do
-    (( j < min || j > max )) && sum+=+$j && A[i]=""
+    (( j < min || j > max )) && sum+=+$j A[i]=""
   done
 done
 echo "16A: $((sum))"
@@ -20,7 +20,7 @@ while read -r name min1 max1 _ min2 max2; do # Read min/max values and field nam
     Cm1[i]=$min1; CM1[i]=$max1
     Cm2[i]=$min2; CM2[i]=$max2
     C[i++]=$name
-done < <(sed -n -e "/ .*:/ s/ /_/;/or/p" "$input")
+done < <(sed -n -e "/ .*:/s/ /_/;/or/p" "$input")
 IFS=$' \n'
 idx=${!C[*]}
 for line in "${B[@]}"; do
@@ -38,9 +38,9 @@ total=1
 while [[ "$oldC" != "${Cf[*]}" ]]; do
   oldC="${Cf[*]}"
   for i in $idx; do
-    if [ ${#Cf[i]} = 1 ] ; then
+    if [[ ${#Cf[i]} == 1 ]]; then
       x=${Cf[i]}
-      [ "${C[i]:0:3}" = dep ] && total+="*${my_ticket[36#$i]}"
+      [[ ${C[i]} = dep* ]] && total+="*${my_ticket[36#$x]}"
       Cf=("${Cf[@]//$x}")
     fi
   done

18.sh

@@ -6,7 +6,7 @@ c() {
     local i sum=0 op='+'
     # shellcheck disable=SC2048
     for i in $*; do
-        if [[ $i = '+' || $i = '*' ]]; then
+        if [[ $i == [+*] ]]; then
             op=$i
         else
             ((sum$op=i))

19.sh

@@ -9,29 +9,30 @@ for i in "${A[@]}"; do
 done
 
 IFS=$' \n'
-REGEX=()
+REGEX=() regex=""
+# shellcheck disable=SC2034,SC2048
 r(){
-    local x=""
-    # shellcheck disable=SC2048
-    for i in $*; do
-      if [ -z "${i/[ab|]}" ]; then
-          x+=$i
-      else
-          [[ -z "${REGEX[$i]}" ]] && REGEX[$i]="($(r "${RULE[$i]}"))"
-          x+="${REGEX[$i]}"
-          #x+="($(r "${RULE[$i]}"))"
-     fi
+    local -n rx=$1; local x="" i
+    for i in ${*:2}; do
+        if [ -z "${i/[ab|]}" ]; then
+            x+=$i
+        else
+            [[ -z "${REGEX[i]}" ]] && r "REGEX[$i]" "${RULE[i]}"
+            x+=${REGEX[i]}
+        fi
     done
-    echo "$x"
+    [[ ${x} == *\|* ]] && x="($x)" # Only brackets if needed
+    rx=$x
 }
-regex=$(r 0)
-echo "19A: $(grep -E -c "^${regex}$" "$input")"
+r regex 0
+printf "19A: "; grep -E -c "^${regex}$" "$input"
 
 #RULE[8]="42 8"
 #RULE[11]="42 31 | 42 11 31"
-r42="$(r 42)"
-r31="$(r 31)"
-r8="${r42}{1,5}"
-r11="${r42}${r31}"
-for n in {2..5}; do r11+="|${r42}{$n}${r31}{$n}"; done
-echo "19B: $(grep -E -c "^($r8)($r11)$" "$input")"
+REGEX[8]="(${REGEX[42]}{1,5})"
+REGEX[11]="${REGEX[42]}${REGEX[31]}"
+for n in {2..5}; do REGEX[11]+="|${REGEX[42]}{$n}${REGEX[31]}{$n}"; done
+REGEX[11]="(${REGEX[11]})"
+REGEX[0]="" regex=""
+r regex 0
+printf "19B: "; grep -E -c "^${regex}$" "$input"

21.sh

@@ -20,5 +20,5 @@ done
 IFS=$'\n'
 ans=$(grep -o ".*(" "$input" | grep -o "[a-z]*" | grep -v -c -F "${B[*]}")
 echo "21A: $ans"
-IFS=,
+IFS=$','
 echo "21B: ${B[*]}"

23.sh

@@ -2,15 +2,15 @@
 A=$(<"${1:-23.txt}")
 i=0
 for _ in {0..99}; do
-c=${A:i:1}
-out=${A:i+1:3}
-A2=${A/$out}
-[ ${#out} -lt 3 ] && A2=${A2:3-${#out}} && out+=${A:0:3-${#out}}
-d=${A:i:1}; ((--d)) || d=9; while [ "${out/$d}" != "${out}" ]; do ((--d)) || d=9; done
-A=${A2/$d/$d${out}}
-#echo $A : $c : $A2-$d:$out
-while [ "${A:i:1}" != "$c" ]; do ((++i==9)) && i=0; done
-((++i==9)) && i=0
+    c=${A:i:1}
+    out=${A:i+1:3}
+    A2=${A/$out}
+    [ ${#out} -lt 3 ] && A2=${A2:3-${#out}} && out+=${A:0:3-${#out}}
+    d=${A:i:1}; ((--d)) || d=9; while [ "${out/$d}" != "${out}" ]; do ((--d)) || d=9; done
+    A=${A2/$d/$d${out}}
+    #echo $A : $c : $A2-$d:$out
+    while [ "${A:i:1}" != "$c" ]; do ((++i==9)) && i=0; done
+    ((++i==9)) && i=0
 done
 echo "23A: ${A/*1}${A/1*}"
 A=$(<"${1:-23.txt}") a=0 b=0 c=0

README.md

@@ -11,8 +11,8 @@ Setting env variable PUREBASH to any value (or giving a second argument) will us
 Description of what I'm doing. Contains spoilers....
 
 ### 01.sh
- 1. Simple grep. Loop through all the numbers looking for 2020-i.
- 2. Double loop through all the numbers looking for 2020-i-j.
+ 1. Use an array as a hash table. Loop through all the numbers looking for 2020-a.
+ 2. Double loop through all the numbers looking for 2020-a-b.
 
 ### 02.sh
  Simple read and string manipulation. Use IFS to split up the min/max and remove the ':'.
@@ -97,7 +97,7 @@ Description of what I'm doing. Contains spoilers....
  2. Just replace "\*" with ")\*(" to change the precedence. Add "(" and ")" to the ends to close off the brackets.
 
 ### 19.sh
- 1. Recursive regex building. Use a cache to speed up previously built regex.
+ 1. Recursive regex building. Use a cache to only build a regex once for each rule.
  2. Cheat a bit and use regex{n} to denote repeated matches.
 
 ### 20.sh