rename repo, subdir for yearly challenges

2020/day18/ex1.bash

@@ -0,0 +1,121 @@
+#!/bin/bash
+#
+# ex1.bash: Advent2020 game, day 18/game 1.
+
+CMD=${0##*/}
+set -o noglob
+
+# shellcheck disable=2034
+declare -a STACK=()
+declare -a LINE=()
+
+function enqueue() {
+    local -n stack="$1"
+    local var="$2"
+    stack=("$var" "${stack[@]}")
+}
+function dequeue() {
+    # shellcheck disable=2178
+    local -n stack="$1"
+    local -n var="$2"
+    local last=$((${#stack[@]} - 1))
+    var=${stack[$last]}
+    unset 'stack[$last]'
+    stack=( "${stack[@]}" )                       # pack
+}
+function eval_op() {
+    # shellcheck disable=2034
+    local -n lvalop="$1" loptop="$2"
+    # shellcheck disable=2034
+    local v v1 v2 op res=-1
+    while ((${#lvalop[@]} > 1)); do
+        dequeue lvalop v1
+        dequeue lvalop v2
+        dequeue loptop op
+        # shellcheck disable=SC1102
+        v=$((v1 "$op" v2))
+        enqueue lvalop "$v"
+        ((res++))
+    done
+    return "$res"
+}
+
+function find_paren() {
+    local -n expr_="$1"
+    local -n var_="$2"
+    local -i i
+    local k val
+    var_=-1
+    for k in "${!expr_[@]}"; do
+        val=${expr_[$k]}
+        [[ $val == '(' ]] && i="$k"
+        if [[ $val == ')' ]]; then
+            # shellcheck disable=SC2034
+            var_="$i"
+            break
+        fi
+    done
+}
+
+function eval_expr() {
+    local -i cur="$2" val len=${#LINE[@]}
+    local op
+    # shellcheck disable=SC2034
+    local -a lstack=() lop=() LINE_=()
+
+    while ((cur < len)); do
+        symbol=${LINE[$cur]}
+        case "$symbol" in
+            [0-9]*)
+                enqueue lstack "${LINE[$cur]}"
+                unset 'LINE[$cur]'
+                ;;
+            \))
+                break
+                ;;
+            [\+\*]*)
+                enqueue lop "${LINE[$cur]}"
+                unset 'LINE[$cur]'
+                ;;
+            *)
+                exit 1
+                ;;
+        esac
+        eval_op lstack lop
+
+        ((cur++))
+    done
+    dequeue lstack val
+    LINE[$cur]="$val"
+    LINE=("${LINE[@]}")                   # pack
+}
+
+declare -i res=0 paren=0
+
+while read -r line; do
+    # cleanup input line, force split around operators and parens
+    line=${line//\*/ * }
+    line=${line//+/ + }
+    line=${line//-/ - }
+    line=${line//\// \/ }
+    line=${line//\(/ \( }
+    line=${line//\)/ \) }
+    read -ra LINE <<< "$line"
+    paren=0
+    while ((${#LINE[@]} > 1 && paren >= 0)); do
+        find_paren LINE paren
+        if (( paren >= 0 )); then
+            unset 'LINE[$paren]'
+            LINE=("${LINE[@]}")                     # pack
+            eval_expr STACK "$paren"
+        fi
+    done
+    if ((${#LINE[@]} > 1)); then
+        eval_expr STACK 0
+    fi
+    ((res+=LINE[0]))
+done
+
+printf "%s : res=%d\n" "$CMD" "$res"
+
+exit 0