1 files changed, 271 insertions, 0 deletions
diff --git a/week01/Exercise4.cpp b/week01/Exercise4.cpp
new file mode 100644
index 0000000..93c8eb9
--- /dev/null
+++ b/week01/Exercise4.cpp
@@ -0,0 +1,271 @@
+#include <iostream>
+#include <cstring>
+#include <cmath>
+
+struct Flight {
+	char takeoffCity[1024];
+	char landingCity[1024];
+
+	int takeoffTime;
+	int landingTime;
+
+	float flightPrice;
+};
+
+void sortByTakeoff(Flight* flights, int N) {
+	for (int i = 0; i < N-1; i++) {
+		for (int j = 0; j < N-1 - i; j++) {
+			if (flights[j].takeoffTime > flights[j+1].takeoffTime) {
+				Flight temp = flights[j];
+				flights[j] = flights[j+1];
+				flights[j+1] = temp;
+			}
+		}
+	}
+}
+
+/*
+ * Подточка а)
+ */
+
+void A(Flight* flights, int N) {
+	for (int i = 0; i < N; i++) {
+		std::cout << flights[i].takeoffCity << " " << flights[i].landingCity << " " << flights[i].flightPrice << std::endl;
+	}
+}
+
+/*
+ * Подточка б), само за най-евтин полет
+ * Това решение е по стила на повечето хора
+ * Решението за най-кратък полет е написано с абстракция in-mind
+ */
+double cheapest(Flight* flights, int N, const char destionationCity[1024], int current, bool* visited, int* flightPath, int fpLength) {
+	flightPath[0] = current;
+
+	if (strcmp(flights[current].landingCity, destionationCity) == 0) {
+		return flights[current].flightPrice;
+	}
+
+	visited[current] = true;
+
+	double cheapestPrice = INFINITY;
+	int* tempPath = new int[fpLength - 1];
+
+	for (int i = 0; i < N; i++) {
+		if (visited[i] == false
+		    && flights[current].landingTime < flights[i].takeoffTime
+		    && strcmp(flights[current].landingCity, flights[i].takeoffCity) == 0)
+		{
+			for (int j = 0; j < fpLength - 1; j++) {
+				tempPath[j] = -1;
+			}
+			double flightsPrice = cheapest(flights, N, destionationCity, i, visited, tempPath, fpLength - 1);
+
+			if (flightsPrice < cheapestPrice) {
+				cheapestPrice = flightsPrice;
+				for (int j = 1; j < fpLength; j++) {
+					flightPath[j] = tempPath[j-1];
+				}
+			}
+		}
+	}
+
+	delete[] tempPath;
+	visited[current] = false;
+	return cheapestPrice + flights[current].flightPrice;
+}
+
+void B1(Flight* flights, int N, char cityToTakeoff[1024], char cityToLand[1024]) {
+	Flight* flightsWithInit = new Flight[N+1];
+
+	strcpy(flightsWithInit[0].landingCity, cityToTakeoff);
+	flightsWithInit[0].takeoffTime = 0;
+	flightsWithInit[0].landingTime = 0;
+	flightsWithInit[0].flightPrice = 0.0;
+
+	for (int i = 0; i < N; i++) {
+		flightsWithInit[i+1] = flights[i];
+	}
+
+	bool* visited = new bool[N+1]{ false };
+	int* flightPath = new int[N+1]{ -1 };
+
+	cheapest(flightsWithInit, N+1, cityToLand, 0, visited, flightPath, N+1);
+
+	std::cout << "Cheapest" << std::endl;
+	for (int i = 1; i <= N; i++) {
+		if (flightPath[i] > -1) {
+			std::cout << flightsWithInit[flightPath[i]].takeoffCity << " "
+			          << flightsWithInit[flightPath[i]].landingCity << " "
+			          << flightsWithInit[flightPath[i]].takeoffTime << " "
+			          << flightsWithInit[flightPath[i]].flightPrice << std::endl;
+		}
+	}
+
+	delete[] flightPath;
+	delete[] visited;
+	delete[] flightsWithInit;
+}
+
+/*
+ * Подточка б), само за най-евтин полет
+ * Решено с абстракция, тоест с една камара помощни функции и структури
+ */
+
+Flight newFlight(const char takeoffCity[1024], const char landingCity[1024], int takeoffTime, int landingTime, float flightPrice) {
+	Flight nf;
+	strcpy(nf.takeoffCity, takeoffCity);
+	strcpy(nf.landingCity, landingCity);
+	nf.takeoffTime = takeoffTime;
+	nf.landingTime = landingTime;
+	nf.flightPrice = flightPrice;
+	return nf;
+}
+bool flightLandsOn(const Flight& fl, const char* city) {
+	return strcmp(fl.landingCity, city) == 0;
+}
+bool flightsCanConnect(const Flight& fl1, const Flight& fl2) {
+	return fl1.landingTime < fl2.takeoffTime
+	       && strcmp(fl1.landingCity, fl2.takeoffCity) == 0;
+}
+int flightDuration(const Flight& fl) {
+	return fl.landingTime - fl.takeoffTime;
+}
+int flightsInbetweenTime(const Flight& fl1, const Flight& fl2) {
+	return fl2.takeoffTime - fl1.landingTime;
+}
+
+struct FlightPath {
+	int* flightsIndecies;
+	int length;
+	int rightmostFreeInd;
+};
+FlightPath newFlightPath(int size) {
+	return { new int[size], size, 0 };
+}
+void freeFlightPath(FlightPath& fp) {
+	delete[] fp.flightsIndecies;
+}
+void clearFlightPath(FlightPath& fp) {
+	for (int i = 0; i < fp.length; i++) {
+		fp.flightsIndecies[i] = -1;
+	}
+}
+void copyFlightPath(FlightPath& destination, int start, const FlightPath& source) {
+	if (start < 0) return;
+
+	for (int i = 0; i + start < destination.length && i < source.length; i++) {
+		destination.flightsIndecies[i + start] = source.flightsIndecies[i];
+	}
+}
+void addToFlightPath(FlightPath& fp, int index) {
+	if (fp.rightmostFreeInd == fp.length) return;
+	fp.flightsIndecies[fp.rightmostFreeInd++] = index;
+}
+void printFlightPath(const FlightPath& fp, int start, const Flight* flights) {
+	for (int i = start; i < fp.length; i++) {
+		if (fp.flightsIndecies[i] > -1) {
+			std::cout << flights[fp.flightsIndecies[i]].takeoffCity << " "
+			          << flights[fp.flightsIndecies[i]].landingCity << " "
+			          << flights[fp.flightsIndecies[i]].takeoffTime << " "
+			          << flights[fp.flightsIndecies[i]].flightPrice << std::endl;
+		}
+	}
+}
+
+struct FlightsArray {
+	Flight* flights;
+	int length;
+	int rightmostFreeInd;
+};
+FlightsArray newFlightArray(int size) {
+	return { new Flight[size], size };
+}
+void freeFlightArray(FlightsArray& fa) {
+	delete[] fa.flights;
+}
+void copyToFlightsArray(FlightsArray& fa, int start, const Flight* flights, int N) {
+	for (int i = 0; i + start < fa.length && i < N; i++) {
+		fa.flights[i + start] = flights[i];
+	}
+}
+void addToFlightsArray(FlightsArray& fa, const Flight& f) {
+	if (fa.length == fa.rightmostFreeInd) return;
+	fa.flights[fa.rightmostFreeInd++] = f;
+}
+
+double shortest(const FlightsArray& fa, const char destinationCity[1024], int current, bool* visited, FlightPath& bestPath) {
+	addToFlightPath(bestPath, current);
+
+	if (flightLandsOn(fa.flights[current], destinationCity)) {
+		return flightDuration(fa.flights[current]);
+	}
+
+	visited[current] = true;
+
+	double shortestDur = INFINITY;
+	FlightPath currentPath = newFlightPath(bestPath.length - 1);
+
+	for (int i = 0; i < fa.length; i++) {
+		if (visited[i] == false && flightsCanConnect(fa.flights[current], fa.flights[i]))
+		{
+			clearFlightPath(currentPath);
+			double flightsDur = shortest(fa, destinationCity, i, visited, currentPath)
+			                    + flightsInbetweenTime(fa.flights[current], fa.flights[i]);
+
+			if (flightsDur < shortestDur) {
+				shortestDur = flightsDur;
+				copyFlightPath(bestPath, 1, currentPath);
+			}
+		}
+	}
+
+	freeFlightPath(currentPath);
+	visited[current] = false;
+
+	return shortestDur + flightDuration(fa.flights[current]);
+}
+
+void B2(Flight* flights, int N, char cityToTakeoff[1024], char cityToLand[1024]) {
+	FlightsArray flightsWithInit = newFlightArray(N+1);
+	addToFlightsArray(flightsWithInit, newFlight("", cityToTakeoff, 0, 0, 0.0));
+
+	copyToFlightsArray(flightsWithInit, 1, flights, N);
+
+	bool* visited = new bool[N+1]{ false };
+	FlightPath shortestPath = newFlightPath(N+1);
+
+	shortest(flightsWithInit, cityToLand, 0, visited, shortestPath);
+
+	std::cout << "Shortest" << std::endl;
+	printFlightPath(shortestPath, 1, flightsWithInit.flights);
+
+	freeFlightPath(shortestPath);
+	freeFlightArray(flightsWithInit);
+	delete[] visited;
+}
+
+int main() {
+	int N;
+	std::cin >> N;
+
+	Flight* flights = new Flight[N];
+	for (int i = 0; i < N; i++) {
+		std::cin >> flights[i].takeoffCity
+		         >> flights[i].landingCity
+		         >> flights[i].takeoffTime
+		         >> flights[i].landingTime
+		         >> flights[i].flightPrice;
+	}
+	sortByTakeoff(flights, N);
+
+	char cityToTakeoff[1024];
+	char cityToLand[1024];
+	std::cin >> cityToTakeoff >> cityToLand;
+
+	A(flights, N);
+	B1(flights, N, cityToTakeoff, cityToLand);
+	B2(flights, N, cityToTakeoff, cityToLand);
+
+	delete[] flights;
+}