From 150e4ba2a7223bc5c0fa52b143990d093f6e6c5f Mon Sep 17 00:00:00 2001
From: Bruno Raoult <braoult@gmail.com>
Date: Sun, 25 Jul 2021 17:12:36 +0200
Subject: [PATCH] starting code for day 20/part 2

---
 2020/day20/ex2.bash | 92 +++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 92 insertions(+)
 create mode 100755 2020/day20/ex2.bash

diff --git a/2020/day20/ex2.bash b/2020/day20/ex2.bash
new file mode 100755
index 0000000..119c36d
--- /dev/null
+++ b/2020/day20/ex2.bash
@@ -0,0 +1,92 @@
+#!/bin/bash
+#
+# ex1.bash: Advent2020 game, day 20/game 2.
+
+CMD=${0##*/}
+set -o noglob
+shopt -s extglob
+
+#declare -A strings
+declare -a strings T R B L RT RR RB RL nums
+declare -a CORNER EDGE CENTRAL
+declare -i count=-1 res=1
+
+while read -r line; do
+    case ${line:0:1} in
+        T*)
+            ((count++))
+            num=${line##* }
+            num=${num%%:}
+            nums+=("$num")
+            ;;
+        \#|.)
+            strings[$count]="${strings[$count]} $line"
+            ;;
+    esac
+done
+((count--))
+
+for key in "${!nums[@]}"; do
+    # shellcheck disable=SC2206
+    str=(${strings[$key]})
+    top="${str[0]}"
+    bottom="${str[9]}"
+    T+=("$top")
+    B+=("$bottom")
+    # find out right and bottom
+    unset left right
+    for ((i=0; i<10; ++i)); do
+        left+=${str[$i]:0:1}
+        right+=${str[$i]: -1:1}
+    done
+    R+=("$right")
+    L+=("$left")
+    unset fliptop flipbottom flipleft flipright
+    for ((i=9; i>=0; --i)); do
+        fliptop+=${top:$i:1}
+        flipbottom+=${bottom:$i:1}
+        flipleft+=${left:$i:1}
+        flipright+=${right:$i:1}
+    done
+    RT+=("$fliptop")
+    RR+=("$flipright")
+    RB+=("$flipbottom")
+    RL+=("$flipleft")
+
+done
+
+ALL="${T[@]} ${R[@]} ${B[@]} ${L[@]} ${RT[@]} ${RR[@]} ${RB[@]} ${RL[@]}"
+ALLSIZE=${#ALL}
+
+for ((i=0; i<${#nums[@]}; ++i)); do
+    count=0
+
+    for t in ${T[$i]} ${R[$i]} ${B[$i]} ${L[$i]}; do
+        # https://stackoverflow.com/questions/26212889/bash-counting-substrings-in-a-string/50601141#50601141
+        S=${ALL//$t}
+        # 10 is line size
+        ((count += (ALLSIZE-${#S})/10))
+    done
+    # 6 is 4 for itself, + 2 for other matching
+    #printf "%s: %d\n" "${nums[$i]}" "$count"
+    case "$count" in
+        6)
+            CORNER+=(${nums[$i]})
+            ((res*=${nums[$i]}))
+            ;;
+        7)
+            EDGE+=(${nums[$i]})
+            ;;
+        8)
+            CENTRAL+=(${nums[$i]})
+            ;;
+    esac
+
+done
+
+printf "CENTRAL[%d]=%s\n" "${#CENTRAL[@]}" "${CENTRAL[*]}"
+printf "EDGE[%d]=%s\n" "${#EDGE[@]}" "${EDGE[*]}"
+printf "CORNER[%d]=%s\n" "${#CORNER[@]}" "${CORNER[*]}"
+printf "%s : res=%d\n" "$CMD" "$res"
+
+exit 0