Day 10

[advent-of-code-2021.git] / day10 / syntax_check.sh

diff --git a/day10/syntax_check.sh b/day10/syntax_check.sh
new file mode 100755 (executable)
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+++ b/day10/syntax_check.sh
@@ -0,0 +1,71 @@
+#!/bin/bash
+
+set -u
+
+filename="${1:-example.txt}"
+exec 3<"$filename"
+
+declare -a brackets
+
+line_number=0
+score=0
+completion_score=0
+
+declare -A bracket_scores=( [")"]=3 ["]"]=57 ["}"]=1197 [">"]=25137 )
+declare -A bracket_complete_score=( [")"]=1 ["]"]=2 ["}"]=3 [">"]=4 )
+declare -a completion_scores
+
+while read -u 3 line; do
+    ((line_number+=1))
+    bad_line=0
+    for (( a=0; a<${#line}; a++ )); do
+        char=${line:$a:1}
+        case $char in
+            "(")
+                brackets+=(")")
+                ;;
+            "<")
+                brackets+=(">")
+                ;;
+            "[")
+                brackets+=("]")
+                ;;
+            "{")
+                brackets+=("}")
+                ;;
+            *)
+                if [ $char != ${brackets[-1]} ]; then
+                    echo "Syntax error, bracket: $char, expected ${brackets[-1]} at offset $a on line $line_number"
+                    ((score+=${bracket_scores[$char]}))
+                    brackets=()
+                    bad_line=1
+                    # we're now skipping the rest of the line
+                    continue 2
+                else
+                    # all good, so remove the last element of the array
+                    unset brackets[-1]
+                fi
+                ;;
+        esac
+    done
+    if [ $bad_line -eq 0 ]; then
+        incomplete_lines+=("$line")
+        completion_score=0
+        # usefully, brackets will still contain the right things
+        while [ ${#brackets[@]} -gt 0 ]; do
+            ((completion_score*=5))
+            ((completion_score+=${bracket_complete_score[${brackets[-1]}]}))
+            unset brackets[-1]
+        done
+        completion_scores+=($completion_score)
+    fi
+done
+
+echo "Score for file: $score"
+
+# sort completion_scores
+IFS=$'\n'
+completion_scores=($(sort -n <<<"${completion_scores[*]}"))
+# now get the middle value
+mid_completion=$((${#completion_scores[@]} / 2))
+echo "Completion score: ${completion_scores[$mid_completion]}"