Day 6 fast

src/days/06/Day06.cpp

@@ -1,9 +1,55 @@
 #include "Day06.h"
+#include <cmath>
 
 Result Day06::Task1() {
-	return Day::Task1();
+	uint64 product = 1;
+
+	for (auto &[time, distance] : parseRecords()){
+		auto [x1, x2] = calculateEdges(double(time), double(distance));
+
+		uint64 wins = uint64(ceil(x2 - 1)) - uint64(x1);
+
+		product *= wins;
+	}
+
+	return to_string(product);
 }
 
 Result Day06::Task2() {
-	return Day::Task2();
-}
+	auto [time, distance] = parseRecord();
+
+	auto [x1, x2] = calculateEdges(double(time), double(distance));
+
+	uint64 wins = uint64(ceil(x2 - 1)) - uint64(x1);
+
+	return to_string(wins);
+}
+
+vector<Day06::Record> Day06::parseRecords() const {
+	vector<Record> records;
+
+	vector<uint64> time = parseInts(input[0].substr(5));
+	vector<uint64> distance = parseInts(input[1].substr(10));
+
+	for (size_t i = 0; i < time.size(); i++)
+		records.emplace_back(time[i], distance[i]);
+
+	return records;
+}
+
+Day06::Record Day06::parseRecord() const {
+	string rawTime = input[0].substr(10);
+	std::erase(rawTime, ' ');
+	string rawDistance = input[1].substr(10);
+	std::erase(rawDistance, ' ');
+	uint64 time = std::stoul(rawTime);
+	uint64 distance = std::stoul(rawDistance);
+	return {time, distance};
+}
+
+pair<double, double> Day06::calculateEdges(double t, double d) {
+	// parabula f(x) = -x² + tx | set it equal to d, calculate x1, x2
+	double x1 = t / 2 - sqrt(t * t / 4 - d);
+	double x2 = t / 2 + sqrt(t * t / 4 - d);
+	return {x1, x2};
+}

src/days/06/Day06.h

@@ -3,8 +3,13 @@
 #include "../../Day.h"
 
 class Day06 : public Day {
+	typedef pair<uint64, uint64> Record;
 protected:
 	Result Task1() override;
 
 	Result Task2() override;
+
+	vector<Record> parseRecords() const;
+	Record parseRecord() const;
+	static pair<double, double> calculateEdges(double t, double d);
 };

src/util.cpp

@@ -44,4 +44,27 @@ bool isDigit(char c, uint8_t &result) {
 bool isDigit(char c) {
 	auto val = c - '0';
 	return val >= 0 && val < 10;
+}
+
+vector<uint64> parseInts(const string &data) {
+	vector<uint64> result;
+
+	uint64 value = 0;
+	bool readingInt = false;
+
+	for (const char c : data){
+		uint8_t digit;
+		if (isDigit(c, digit)) {
+			value = value * 10 + digit;
+			readingInt = true;
+		} else if (readingInt){
+			readingInt = false;
+			result.push_back(value);
+			value = 0;
+		}
+	}
+	if (readingInt)
+		result.push_back(value);
+
+	return result;
 }

src/util.h

@@ -28,4 +28,6 @@ vector<string> split(const string &data, char c);
 
 bool isDigit(char c, uint8_t &result);
 
-bool isDigit(char c);
+bool isDigit(char c);
+
+vector<uint64> parseInts(const string &data);