ollien
/
advent-of-code-2020
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Convert day 19 part 1 to use regular expressions

master
Nick Krichevsky 2020-12-20 23:16:59 -05:00
parent ae8847bdd1
commit 196a679dc3
1 changed files with 49 additions and 57 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

88
day19/day19.cpp
View File

@ -1,3 +1,4 @@
#include <folly/Format.h>
#include <folly/String.h>
#include <fstream>
@ -7,6 +8,7 @@
#include <memory>
#include <numeric>
#include <optional>
#include <regex>
#include <string>
#include <vector>
@ -92,10 +94,9 @@ MultiGrammarEntry parseSinglePattern(const std::string &rawPattern) {
return patternComponents;
}
std::unordered_map<int, AlternatableMultiGrammarEntry> parseGrammar(const std::vector<std::string> &patterns) {
std::unordered_map<int, AlternatableMultiGrammarEntry> grammar;
std::transform(
patterns.cbegin(), patterns.cend(), std::inserter(grammar, grammar.end()), [](const std::string &patternLine) {
std::unordered_multimap<int, MultiGrammarEntry> parseGrammar(const std::vector<std::string> &patterns) {
std::unordered_multimap<int, MultiGrammarEntry> grammar;
for (const std::string &patternLine : patterns) {
auto colonIndex = patternLine.find(":");
std::string rawIndex = patternLine.substr(0, colonIndex);
int patternIndex = std::stoi(rawIndex);
@ -103,65 +104,56 @@ std::unordered_map<int, AlternatableMultiGrammarEntry> parseGrammar(const std::v
// An extra +1 on the colon index to get rid of the space after the colon
folly::split(ALTERNATING_DELIM, patternLine.substr(colonIndex + 2), rawAlternations);
AlternatableMultiGrammarEntry entries;
std::transform(
rawAlternations.cbegin(), rawAlternations.cend(), std::back_inserter(entries), parseSinglePattern);
return std::pair<int, AlternatableMultiGrammarEntry>(patternIndex, entries);
rawAlternations.cbegin(),
rawAlternations.cend(),
std::inserter(grammar, grammar.end()),
[patternIndex](const std::string &pattern) {
return std::make_pair(patternIndex, parseSinglePattern(pattern));
});
}
return grammar;
}
int matchesHowManyChars(
const std::unordered_map<int, AlternatableMultiGrammarEntry> &grammar, const std::string_view toParse, int rule = 0,
int depth = 0) {
auto indentation = std::string(depth, '|');
std::cout << indentation << "Working on " << toParse << std::endl;
AlternatableMultiGrammarEntry ruleAlternations = grammar.at(rule);
std::optional<std::pair<MultiGrammarEntry, int>> best;
for (const MultiGrammarEntry &alternation : ruleAlternations) {
int numMatched = 0;
int i = 0;
for (auto entryIt = alternation.cbegin(); entryIt != alternation.cend(); (++entryIt, i++)) {
GrammarEntry entry = *entryIt;
int ruleMatchCount;
if (entry.isLookup()) {
std::cout << indentation << "Checking rule " << entry.getIndex() << std::endl;
ruleMatchCount = matchesHowManyChars(grammar, toParse.substr(numMatched), entry.getIndex(), depth + 1);
std::string convertToRegularExpression(const std::unordered_multimap<int, MultiGrammarEntry> &grammar, int rule) {
std::vector<std::string> expressions;
auto ruleIterators = grammar.equal_range(rule);
std::transform(
ruleIterators.first,
ruleIterators.second,
std::back_inserter(expressions),
[&grammar](const std::pair<int, MultiGrammarEntry> &entry) {
MultiGrammarEntry alternative = entry.second;
std::string expression;
for (const GrammarEntry &grammarEntry : alternative) {
if (grammarEntry.isLookup()) {
expression += convertToRegularExpression(grammar, grammarEntry.getIndex());
} else {
std::cout << indentation << "Checking rule " << entry.getValue() << std::endl;
char toMatch = toParse.at(i);
char ruleValue = entry.getValue();
ruleMatchCount = (toMatch == ruleValue);
}
std::cout << indentation << "Result: " << numMatched << std::endl;
if (!ruleMatchCount) {
break;
}
numMatched += ruleMatchCount;
}
std::cout << indentation << "Full result: " << numMatched << std::endl;
if (!best || numMatched > best->second) {
best = std::pair<MultiGrammarEntry, int>(alternation, numMatched);
expression += grammarEntry.getValue();
}
}
if (!best) {
return 0;
return expression;
});
if (expressions.size() == 1) {
return expressions.at(0);
} else {
return folly::format("({})", folly::join("|", expressions)).str();
}
}
return best->second;
std::regex convertToRegularExpression(const std::unordered_multimap<int, MultiGrammarEntry> &grammar) {
auto rawRegularExpression = convertToRegularExpression(grammar, 0);
return std::regex(rawRegularExpression);
}
int part1(const std::vector<std::string> &patterns, const std::vector<std::string> &testStrings) {
std::unordered_map<int, AlternatableMultiGrammarEntry> grammar = parseGrammar(patterns);
return std::count_if(testStrings.cbegin(), testStrings.cend(), [&grammar](const std::string &testString) {
return matchesHowManyChars(grammar, testString) == testString.length();
std::unordered_multimap<int, MultiGrammarEntry> grammar = parseGrammar(patterns);
std::regex inputRegex = convertToRegularExpression(grammar);
return std::count_if(testStrings.cbegin(), testStrings.cend(), [&inputRegex](const std::string &testString) {
return std::regex_match(testString, inputRegex);
});
}