diff --git a/2020/day23/ex1.bash b/2020/day23/ex1.bash
index 9e6b0ef..742f0c8 100755
--- a/2020/day23/ex1.bash
+++ b/2020/day23/ex1.bash
@@ -6,171 +6,49 @@ CMD=${0##*/}
 shopt -s extglob
 set -o noglob
 
-#declare -a INPUT
-declare rev="98765432198765"
-runs=${1:-10}
+declare -A next                                   # next[i] is cup right to i
+declare -i end runs cup _cup
+
 read -r str
-#[[ "$str" =~ ${str//?/(.)} ]]
-#INPUT=("${BASH_REMATCH[@]:1}")
-#printf "INPUT=%s \n" "${INPUT[*]}"
+tmp="${str//?()/x}"
+tmp=${tmp#x}
+IFS=x read -ra array <<< "$tmp"
 
-pos() {
-    local -n _pos=$1
-    local c=$2 s=$3
-    local -i i
-    for ((i=0; i<9; ++i)); do
-        [[ ${s:i:1} = "$c" ]] && break
-    done
-    printf "pos(%s, %s)=%d\n" "$s" "$c" "$i"
-    _pos=$((i+1))
-}
-
-# charpos - get cup position in a string
-# $1 reference of variable to store the position
-# $2: The string
-# $3: The cup to find
-#
-# @Return: cup position
-# example: charpos "987654321" "9" will return 0
-charpos() {
-    local -n _res="$1"
-    local left="${2%%"$3"*}"
-    # printf " charpos(%s,%s)=%d " "$2" "$3" "${#left}"
-    [[ "$left" = "$2" ]] && _res=-1 || _res=${#left}
-}
-
-# destcup - get insertion position
-# $1: reference of variable to store the cup position in string
-# $2: current cup
-# $3: The string
-#
-# @Return: the next cup
-# example: nextchar "987654321" "9" will return 8
-destcup() {
-    local -n _pos="$1"
-    local _cup="$2" _str="$3"
-    #(( _cup-- ))
-    printf "destcup str=%s _pos=%d cup=%d\n" "$_str" "$_pos" "$_cup"
-    while (( _cup = (_cup + 8) % 9))
-          (( _cup == 0 )) && (( _cup = 9 ))
-          printf "trying %d in %s ..." "$_cup" "$_str"
-          charpos _pos "$_str" "$_cup"
-          printf " pos=%d " "$_pos"
-          (( _pos == -1 )); do
-        echo fail
-    done
-    echo ok
-}
-
-# nextcup - get next cup in string
-# $1: reference of current cup
-# $2: The string
-#
-# @Return: the next cup
-nextcup() {
-    local -n _cup="$1"
-    local _str="$2$2"
-    _str=${_str#*"$_cup"}
-    # printf "str=%s\n" "$_str"
-    _cup=${_str:0:1}
-}
-
-# pickup - get the pickup string after current one
-# $1 reference of variable to store the pickup string
-# $2: reference of string string
-# $3: The current cup
-#
-# @Return: the pickup string
-# example: charpos "987654321" "2" will return "198"
-pickup() {
-    local -n _pick="$1" _str="$2"
-    local -i _pos
-    local tmp="$_str$_str"
-    #printf "STR2= %s %s\n" "$2" "$_str"
-    charpos _pos "$_str" "$3"
-    printf " str=%s _pos(%s)=%d->" "$_str" "$3" "$_pos"
-    (( _pos = (_pos + 1) % 9 ))
-    _pick="${tmp:_pos:3}"
-    tmp=${tmp//[$_pick]}
-    _str=${tmp:0:6}
-    printf "%d = pick=%s str=%s\n" "$_pos" "$_pick" "$_str"
-}
-
-declare -i res pos=0 cup=${str:0:1}
-declare pick
-#printf "BEFORE str=%s cup=%s pos=%d\n" "$str" "$cup" "$pos"
-#nextcup cup pos "$str"
-#printf "AFTER str=%s cup=%s pos=%d\n" "$str" "$cup" "$pos"
-
-for ((i = 1; i <= 100; ++i)); do
-    printf "\nloop=%d str=%s cup=%s pos=%d\n" "$i" "$str" "$cup" "$pos"
-    pickup pick str "$cup"
-    printf "AFTER1 str=%s pick=%s cup=%s pos=%d\n" "$str" "$pick" "$cup" "$pos"
-    destcup pos "$cup" "$str"
-    printf "AFTER2 str=%s pick=%s cup=%s pos=%d\n" "$str" "$pick" "$cup" "$pos"
-    #insert str "$pick" "$pos"
-    str="${str:0:pos+1}$pick${str:pos+1}"
-    printf "newstr=%s pick=%s\n" "$str" "$pick"
-    nextcup cup "$str"
-    printf "next cup=%s\n" "$cup"
-    #charpos res "$str" "$i"
-    #nextchar next "$str" "$i"
-    #printf "a(%s, %d)=%d next=%s\n" "$str" "$i" "$res" "$next"
+cup=${array[0]}
+end=${#array[@]}
+runs=100
 
+_cup=$cup
+# initialize the next array with input cups
+for _next in "${array[@]:1}"; do
+    next[$_cup]=$_next
+    _cup=$_next
 done
-res="${str#*1}${str%1*}"
-printf "%s: res=%d\n" "$CMD" "$res"
+next[$_cup]=$cup                                  # close the ring
+
+_cup=$cup
+
+declare -i _1st _2nd _3rd dest
+# make the moves: a simple sub-linked list operation.
+for ((i = 1; i <= runs; ++i)); do
+    _1st="${next[$cup]}"
+    _2nd="${next[$_1st]}"
+    _3rd="${next[$_2nd]}"
+    dest=$cup
+    while
+        (( --dest > 0 )) || dest=$end
+        (( dest == _1st || dest == _2nd || dest == _3rd ))
+    do :; done
+    (( tmp=next[$dest], next[$dest]=_1st, next[$cup]=next[$_3rd], next[$_3rd]=tmp ))
+    (( cup=next[$cup] ))
+done
+
+res=""
+_cup=1
+while
+    (( _cup = next[$_cup] ))
+    res+="$_cup"
+    (( next[$_cup] != 1 ))
+do :; done
+printf "%s: res=%s\n" "$CMD" "$res"
 exit 0
-
-# move - rune a move
-# $1: The input string (by address)
-# $2: The current cup
-#
-# @Return: The next cup
-move() {
-
-    :
-}
-
-run() {
-    local -i l="$1" p="$2" pos
-    local str="$3"
-    local str2 o c
-
-    while ((--l)); do
-        printf "%s move %d --\n" "--" $(($1 - l))
-        printf "cups=%s\n" "$str"
-        printf "pos=%s\n" "$p"
-        #
-        #printf "cups:"
-        #for ((j=0; j<9; ++j)); do
-
-        #printf "str2=%s\n" "$str2"
-
-        o=${str2:p+1:3}
-        c=${str2:p:1}
-        # remove the 3 cups
-        str2=${str2//$o/}
-        rev1=${rev#*$c}
-        printf "c=%s\npick up=%s\nstr2=%s\n" "$c" "$o" "$str2"
-        printf "rev1=%s\n" "$rev1"
-
-        # find destination cup
-        for ((i=0; i<4; ++i)); do
-            c2=${rev1:i:1}
-            printf "testing %c in %s\n" "$c2" "$o"
-            [[ $o =~ .*$c2.* ]] || break
-        done
-        printf "destination=%s\n" "$c2"
-        pos pos "$c2" "$str2"
-        str2=${str2:0:$pos}$o${str2:$pos}
-        #str2=${str2/$c2/$c2$o}
-        #str2=${str2/$c2/$c2$o}
-
-        printf "str2=%s\n" "$str2"
-        str=${str2:0:9}
-
-        ((++p==9)) && p=0
-        printf "new str=%s\n\n" "$str"
-    done
-}