add bash solution for day2

src/day_2.sh

@@ -0,0 +1,54 @@
+#!/usr/bin/env bash
+unset PATH
+BASE='.*';until [[ "$(eval "echo $BASE")" =~ \.git ]]; do BASE="../$BASE"; done;BASE="${BASE/'*'}"
+source "$BASE/utils.sh"
+
+INPUT="$(<"$BASE/data/day_2.txt")"
+
+declare -A COMBINATION_TO_POINTS=(
+  ['A X']=3
+  ['A Y']=6
+  ['A Z']=0
+  ['B X']=0
+  ['B Y']=3
+  ['B Z']=6
+  ['C X']=6
+  ['C Y']=0
+  ['C Z']=3
+)
+
+declare -A SHOULD_PLAY=(
+  ['A X']=Z
+  ['A Y']=X
+  ['A Z']=Y
+  ['B X']=X
+  ['B Y']=Y
+  ['B Z']=Z
+  ['C X']=Y
+  ['C Y']=Z
+  ['C Z']=X
+)
+
+declare -A SCORES=([X]=1 [Y]=2 [Z]=3)
+
+p1() {
+  mapfile -t scores <<< "$(
+    while read -r i; do
+      echo $(( COMBINATION_TO_POINTS[$i] + SCORES[${i:2}] ))
+    done <<< "$1"
+  )"
+  utils.sum "${scores[@]}"
+}
+
+p2() {
+  mapfile -t scores <<< "$(
+    while read -r i; do
+      i="${i::1} ${SHOULD_PLAY["$i"]}"
+      echo $(( COMBINATION_TO_POINTS[$i] + SCORES[${i:2}] ))
+    done <<< "$1"
+  )"
+  utils.sum "${scores[@]}"
+}
+
+p1 "$INPUT"
+p2 "$INPUT"