diff --git a/.vscode/launch.json b/.vscode/launch.json
index 356814a..21292a0 100644
--- a/.vscode/launch.json
+++ b/.vscode/launch.json
@@ -29,8 +29,8 @@
                 "output0.txt",
                 "output1.txt",
                 "output2.txt",
-                "516-951-1561",
-                "request",
+                "860-680-4504",
+                "cancel",
                 "debug"
             ],
             "cwd": "${fileDirname}",
diff --git a/hws/ride_sharing/Driver.cpp b/hws/ride_sharing/Driver.cpp
new file mode 100644
index 0000000..6fc7264
--- /dev/null
+++ b/hws/ride_sharing/Driver.cpp
@@ -0,0 +1,72 @@
+#include "Driver.h"
+#include <sstream>
+
+Driver::Driver() : age(0), rating(0.0), latitude(0.0), longitude(0.0) {}
+
+Driver::Driver(const std::string &fName, const std::string &lName,
+               const std::string &gen, int a, const std::string &phone,
+               double r, double lat, double lon,
+               const std::string &vehType, const std::string &state,
+               const std::string &rF, const std::string &rL,
+               const std::string &rP)
+ : firstName(fName), lastName(lName), gender(gen), age(a),
+   phoneNumber(phone), rating(r), latitude(lat), longitude(lon),
+   vehicleType(vehType), currentState(state),
+   riderFirstName(rF), riderLastName(rL), riderPhoneNumber(rP) {}
+
+//getters
+const std::string& Driver::getFirstName() const { return firstName; }
+const std::string& Driver::getLastName() const { return lastName; }
+const std::string& Driver::getGender() const { return gender; }
+int Driver::getAge() const { return age; }
+const std::string& Driver::getPhoneNumber() const { return phoneNumber; }
+double Driver::getRating() const { return rating; }
+double Driver::getLatitude() const { return latitude; }
+double Driver::getLongitude() const { return longitude; }
+const std::string& Driver::getVehicleType() const { return vehicleType; }
+const std::string& Driver::getCurrentState() const { return currentState; }
+const std::string& Driver::getRiderFirstName() const { return riderFirstName; }
+const std::string& Driver::getRiderLastName() const { return riderLastName; }
+const std::string& Driver::getRiderPhoneNumber() const { return riderPhoneNumber; }
+
+//setters
+void Driver::setCurrentState(const std::string &state) {
+    currentState = state;
+}
+
+void Driver::setRiderInfo(const std::string &rf, const std::string &rl, const std::string &rp) {
+    riderFirstName = rf;
+    riderLastName = rl;
+    riderPhoneNumber = rp;
+}
+
+std::string Driver::toFileString() const {
+    //Sandra
+    //Huang
+    //Female
+    //25
+    //853-977-5304  
+    //3.1
+    //40.4269
+    //-73.0753
+    //Standard
+    //On_the_way_to_pickup
+    //Michael
+    //Richard
+    //445-915-1645
+    std::ostringstream oss;
+    oss << firstName << " "
+        << lastName << " "
+        << gender << " "
+        << age << " "
+        << phoneNumber << " "
+        << rating << " "
+        << latitude << " "
+        << longitude << " "
+        << vehicleType << " "
+        << currentState << " "
+        << (riderFirstName.empty() ? "null" : riderFirstName) << " "
+        << (riderLastName.empty() ? "null" : riderLastName) << " "
+        << (riderPhoneNumber.empty() ? "null" : riderPhoneNumber);
+    return oss.str();
+}
diff --git a/hws/ride_sharing/Driver.h b/hws/ride_sharing/Driver.h
new file mode 100644
index 0000000..0153910
--- /dev/null
+++ b/hws/ride_sharing/Driver.h
@@ -0,0 +1,54 @@
+#ifndef __DRIVER_H
+#define __DRIVER_H
+
+#include <string>
+
+class Driver {
+private:
+    std::string firstName;
+    std::string lastName;
+    std::string gender;
+    int age;
+    std::string phoneNumber;
+    double rating;
+    double latitude;
+    double longitude;
+    std::string vehicleType;
+    std::string currentState;
+    //rider's info
+    std::string riderFirstName;
+    std::string riderLastName;
+    std::string riderPhoneNumber;
+
+public:
+    //init
+    Driver();
+    Driver(const std::string &firstName, const std::string &lastName,
+           const std::string &gender, int age, const std::string &phoneNumber,
+           double rating, double latitude, double longitude,
+           const std::string &vehicleType, const std::string &currentState,
+           const std::string &riderFirstName, const std::string &riderLastName,
+           const std::string &riderPhoneNumber);
+
+    //getters & setters
+    const std::string& getFirstName() const;
+    const std::string& getLastName() const;
+    const std::string& getGender() const;
+    int getAge() const;
+    const std::string& getPhoneNumber() const;
+    double getRating() const;
+    double getLatitude() const;
+    double getLongitude() const;
+    const std::string& getVehicleType() const;
+    const std::string& getCurrentState() const;
+    const std::string& getRiderFirstName() const;
+    const std::string& getRiderLastName() const;
+    const std::string& getRiderPhoneNumber() const;
+
+    void setCurrentState(const std::string &state);
+    void setRiderInfo(const std::string &rf, const std::string &rl, const std::string &rp);
+    //return a string representation of the driver
+    std::string toFileString() const;
+};
+
+#endif
diff --git a/hws/ride_sharing/README.txt b/hws/ride_sharing/README.txt
index cb62f72..8018296 100644
--- a/hws/ride_sharing/README.txt
+++ b/hws/ride_sharing/README.txt
@@ -1,7 +1,7 @@
 HOMEWORK 2: Ride Sharing
 
 
-NAME:  < insert name >
+NAME:  Jinshan Zhou
 
 
 COLLABORATORS AND OTHER RESOURCES:
@@ -10,17 +10,17 @@ List the names of everyone you talked to about this assignment
 LMS, etc.), and all of the resources (books, online reference
 material, etc.) you consulted in completing this assignment.
 
-< insert collaborators / resources >
+<sstream>, <iomanip> usage cases online. And one of my classmates - Qijun Lu
 
 Remember: Your implementation for this assignment must be done on your
 own, as described in "Academic Integrity for Homework" handout.
 
 
-ESTIMATE OF # OF HOURS SPENT ON THIS ASSIGNMENT:  < insert # hours >
+ESTIMATE OF # OF HOURS SPENT ON THIS ASSIGNMENT:  12 hr
 
 
 MISC. COMMENTS TO GRADER:
-(optional, please be concise!)
+Ignore the debug codes. To enable it, take `debug` as the last argument.
 
 
 ## Reflection and Self Assessment
@@ -33,4 +33,9 @@ What parts of the assignment did you find challenging? Is there anything that
 finally "clicked" for you in the process of working on this assignment? How well
 did the development and testing process go for you?
 
-< insert reflection >
+The complexity of this assignment has significantly increased. I attempted
+to write the code directly but encountered unprecedented difficulties, and
+the code became increasingly messy. Eventually, I had no choice but to draw a
+flowchart and then gradually implement the code based on it. This means that
+textual descriptions are not as clear as diagrams, so next time I will read
+the documentation first, design the structure properly, and then start coding.
diff --git a/hws/ride_sharing/Rider.cpp b/hws/ride_sharing/Rider.cpp
new file mode 100644
index 0000000..195aa4e
--- /dev/null
+++ b/hws/ride_sharing/Rider.cpp
@@ -0,0 +1,86 @@
+#include "Rider.h"
+#include <sstream>
+
+Rider::Rider()
+ : age(0), rating(0.0), pickupLatitude(0.0), pickupLongitude(0.0),
+   dropoffLatitude(0.0), dropoffLongitude(0.0) {}
+
+Rider::Rider(const std::string &fName, const std::string &lName,
+             const std::string &gen, int a, const std::string &phone,
+             double r, const std::string &pickupLocName, double pickupLat, double pickupLon,
+             const std::string &dropoffLocName, double dropoffLat, double dropoffLon,
+             const std::string &vPref, const std::string &state,
+             const std::string &dF, const std::string &dL, const std::string &dP)
+ : firstName(fName), lastName(lName), gender(gen), age(a),
+   phoneNumber(phone), rating(r),
+   pickupLocationName(pickupLocName), pickupLatitude(pickupLat), pickupLongitude(pickupLon),
+   dropoffLocationName(dropoffLocName), dropoffLatitude(dropoffLat), dropoffLongitude(dropoffLon),
+   vehiclePref(vPref), currentState(state),
+   driverFirstName(dF), driverLastName(dL), driverPhoneNumber(dP) {}
+
+const std::string& Rider::getFirstName() const { return firstName; }
+const std::string& Rider::getLastName() const { return lastName; }
+const std::string& Rider::getGender() const { return gender; }
+int Rider::getAge() const { return age; }
+const std::string& Rider::getPhoneNumber() const { return phoneNumber; }
+double Rider::getRating() const { return rating; }
+const std::string& Rider::getPickupLocationName() const { return pickupLocationName; }
+double Rider::getPickupLatitude() const { return pickupLatitude; }
+double Rider::getPickupLongitude() const { return pickupLongitude; }
+const std::string& Rider::getDropoffLocationName() const { return dropoffLocationName; }
+double Rider::getDropoffLatitude() const { return dropoffLatitude; }
+double Rider::getDropoffLongitude() const { return dropoffLongitude; }
+const std::string& Rider::getVehiclePref() const { return vehiclePref; }
+const std::string& Rider::getCurrentState() const { return currentState; }
+const std::string& Rider::getDriverFirstName() const { return driverFirstName; }
+const std::string& Rider::getDriverLastName() const { return driverLastName; }
+const std::string& Rider::getDriverPhoneNumber() const { return driverPhoneNumber; }
+
+void Rider::setCurrentState(const std::string &state) {
+    currentState = state;
+}
+
+void Rider::setDriverInfo(const std::string &df, const std::string &dl, const std::string &dp) {
+    driverFirstName = df;
+    driverLastName = dl;
+    driverPhoneNumber = dp;
+}
+
+std::string Rider::toFileString() const {
+    //Isabella
+    //Richard
+    //Female
+    //39
+    //301-144-6533
+    //3.2
+    //Top_of_the_Rock
+    //40.7593 -73.979
+    //Gowanus
+    //40.6733
+    //-73.99
+    //Economy
+    //Ready_to_request
+    //null
+    //null
+    //null
+    std::ostringstream oss;
+    oss << firstName << " "
+        << lastName << " "
+        << gender << " "
+        << age << " "
+        << phoneNumber << " "
+        << rating << " "
+        << pickupLocationName << " "
+        << pickupLatitude << " "
+        << pickupLongitude << " "
+        << dropoffLocationName << " "
+        << dropoffLatitude << " "
+        << dropoffLongitude << " "
+        << vehiclePref << " "
+        << currentState << " "
+        << (driverFirstName.empty() ? "null" : driverFirstName) << " "
+        << (driverLastName.empty() ? "null" : driverLastName) << " "
+        << (driverPhoneNumber.empty() ? "null" : driverPhoneNumber);
+
+    return oss.str();
+}
diff --git a/hws/ride_sharing/Rider.h b/hws/ride_sharing/Rider.h
new file mode 100644
index 0000000..999e0dd
--- /dev/null
+++ b/hws/ride_sharing/Rider.h
@@ -0,0 +1,62 @@
+#ifndef __RIDER_H
+#define __RIDER_H
+
+#include <string>
+
+class Rider {
+private:
+    std::string firstName;
+    std::string lastName;
+    std::string gender;
+    int age;
+    std::string phoneNumber;
+    double rating;
+    std::string pickupLocationName;
+    double pickupLatitude;
+    double pickupLongitude;
+    std::string dropoffLocationName;
+    double dropoffLatitude;
+    double dropoffLongitude;
+    std::string vehiclePref;
+    std::string currentState;
+    //driver's info
+    std::string driverFirstName;
+    std::string driverLastName;
+    std::string driverPhoneNumber;
+
+public:
+    //init
+    Rider();
+    Rider(const std::string &fName, const std::string &lName,
+          const std::string &gen, int a, const std::string &phone,
+          double r, const std::string &pickupLocName, double pickupLat, double pickupLon,
+          const std::string &dropoffLocName, double dropoffLat, double dropoffLon,
+          const std::string &vehiclePref, const std::string &state,
+          const std::string &dF, const std::string &dL, const std::string &dP);
+
+    //getters & setters
+    const std::string& getFirstName() const;
+    const std::string& getLastName() const;
+    const std::string& getGender() const;
+    int getAge() const;
+    const std::string& getPhoneNumber() const;
+    double getRating() const;
+    const std::string& getPickupLocationName() const;
+    double getPickupLatitude() const;
+    double getPickupLongitude() const;
+    const std::string& getDropoffLocationName() const;
+    double getDropoffLatitude() const;
+    double getDropoffLongitude() const;
+    const std::string& getVehiclePref() const;
+    const std::string& getCurrentState() const;
+    const std::string& getDriverFirstName() const;
+    const std::string& getDriverLastName() const;
+    const std::string& getDriverPhoneNumber() const;
+
+    void setCurrentState(const std::string &state);
+    void setDriverInfo(const std::string &df, const std::string &dl, const std::string &dp);
+    //return a string representation of the rider
+    std::string toFileString() const;
+};
+
+#endif
diff --git a/hws/ride_sharing/nyride.cpp b/hws/ride_sharing/nyride.cpp
new file mode 100644
index 0000000..5e4c08b
--- /dev/null
+++ b/hws/ride_sharing/nyride.cpp
@@ -0,0 +1,391 @@
+//An implement of CSCI-1200 HW2 Ride Sharing
+//Author: Jinshan Zhou
+//Date: 2025/1/20
+//#include <algorithm>
+//#include <cstdlib>
+#include <cmath>
+#include <vector>
+#include <fstream>
+#include <sstream>
+#include <string>
+#include <iostream>
+#include <iomanip>
+
+#include "Driver.h"
+#include "Rider.h"
+
+void debug_print(const std::string &msg) {
+    std::cout << "DEBUG: " << msg << std::endl;
+}
+
+bool isPhoneNumberValid(const std::string &phone)
+{
+    if (phone.size() != 12) return false;
+    //xxx-xxx-xxxx
+    for (int i = 0; i < 12; i++) {
+        if (i == 3 || i == 7) {
+            if (phone[i] != '-') return false;
+        } else {
+            if (!std::isdigit((unsigned char)phone[i])) return false;
+        }
+    }
+    return true;
+}
+
+void loadDrivers(std::ifstream &ifs, std::vector<Driver> &drivers) {
+    //read the file line by line, total of 13
+    while (!ifs.eof()) {
+        std::string fName, lName, gender, phone, vehicleType, state;
+        std::string rF, rL, rP;
+        int age;
+        double rating, lat, lon;
+        ifs >> fName >> lName >> gender >> age >> phone >> rating >> lat >> lon
+            >> vehicleType >> state >> rF >> rL >> rP;
+        if (!ifs.fail()) {
+            //change "null" to empty string
+            if (rF == "null") rF = "";
+            if (rL == "null") rL = "";
+            if (rP == "null") rP = "";
+            //create driver
+            Driver d(fName, lName, gender, age, phone, rating, lat, lon,
+                     vehicleType, state, rF, rL, rP);
+            drivers.push_back(d);
+        }
+    }
+    ifs.close();
+}
+
+void loadRiders(std::ifstream &ifs, std::vector<Rider> &riders) {
+    //read the file line by line, total of 17
+    while (!ifs.eof()) {
+        std::string fName, lName, gender, phone, pickupLoc, dropoffLoc, vPref, state;
+        std::string dF, dL, dP;
+        int age;
+        double rating, pickupLat, pickupLon, dropoffLat, dropoffLon;
+        ifs >> fName >> lName >> gender >> age >> phone >> rating
+            >> pickupLoc >> pickupLat >> pickupLon
+            >> dropoffLoc >> dropoffLat >> dropoffLon
+            >> vPref >> state
+            >> dF >> dL >> dP;
+        if (!ifs.fail()) {
+            //fill null with empty string
+            if (dF == "null") dF = "";
+            if (dL == "null") dL = "";
+            if (dP == "null") dP = "";
+            //create rider
+            Rider r(fName, lName, gender, age, phone, rating,
+                    pickupLoc, pickupLat, pickupLon,
+                    dropoffLoc, dropoffLat, dropoffLon,
+                    vPref, state, dF, dL, dP);
+            riders.push_back(r);
+        }
+    }
+    ifs.close();
+}
+
+std::ifstream loadFile(const std::string &filename) {
+    //read file and return ifstream
+    std::ifstream ifs(filename);
+    if (!ifs) {
+        std::cerr << "Error opening file: " << filename << std::endl;
+        exit(1);
+    }
+    return ifs;
+}
+
+void saveFile(const std::string &filename, const std::string &msg) {
+    std::ofstream ofs(filename);
+    if (!ofs) {
+        std::cerr << "Error opening file: " << filename << std::endl;
+        exit(1);
+    }
+    ofs << msg;
+    ofs.close();
+}
+
+void exportDrivers(const std::string &filename, const std::vector<Driver> &drivers) {
+    //save drivers to file
+    std::ofstream ofs(filename);
+    if (!ofs) {
+        std::cerr << "Error opening output file: " << filename << std::endl;
+        return;
+    }
+    for (int i = 0; i < (int)drivers.size(); i++) {
+        const Driver &d = drivers[i];
+        ofs << d.toFileString() << "\n";
+    }
+    ofs.close();
+}
+
+void exportRiders(const std::string &filename, const std::vector<Rider> &riders) {
+    //save riders to file
+    std::ofstream ofs(filename);
+    if (!ofs) {
+        std::cerr << "Error opening output file: " << filename << std::endl;
+        return;
+    }
+    for (int i = 0; i < (int)riders.size(); i++) {
+        const Rider &r = riders[i];
+        ofs << r.toFileString() << "\n";
+    }
+    ofs.close();
+}
+
+// calculate the distance between two coordinates using Haversine formula
+double calculateDistance(double lat1, double lon1, double lat2, double lon2) {
+    const double radiusOfEarth = 6371.0; // Earth's radius in kilometers
+    // convert latitude and longitude from degrees to radians
+    lat1 *= M_PI / 180.0;
+    lon1 *= M_PI / 180.0;
+    lat2 *= M_PI / 180.0;
+    lon2 *= M_PI / 180.0;
+    // Haversine formula
+    double dLat = lat2 - lat1;
+    double dLon = lon2 - lon1;
+    double a = sin(dLat / 2.0) * sin(dLat / 2.0) + cos(lat1) * cos(lat2) * sin(dLon / 2.0) * sin(dLon / 2.0);
+    double c = 2.0 * atan2(sqrt(a), sqrt(1.0 - a));
+    // distance in kilometers
+    double distanceKM = radiusOfEarth * c;
+    // convert it to distance in miles
+    double distanceMiles = distanceKM * 0.621371;
+
+    return distanceMiles;
+}
+
+int findClosestDriver(const std::vector<Driver> &drivers,
+                      const Rider &rider) {
+    double minDistance = 1e9;
+    int bestIndex = -1;
+    for (int i = 0; i < (int)drivers.size(); i++) {
+        const Driver &drv = drivers[i];
+        if (drv.getCurrentState() == "Available" &&
+            drv.getVehicleType() == rider.getVehiclePref()) {
+            double dist = calculateDistance(drv.getLatitude(), drv.getLongitude(),
+                                            rider.getPickupLatitude(), rider.getPickupLongitude());
+            if (dist < minDistance) {
+                minDistance = dist;
+                bestIndex = i;
+            }
+        }
+    }
+    return bestIndex;
+}
+
+int findRiderIndexByPhone(const std::vector<Rider> &riders, const std::string &phone) {
+    for (int i = 0; i < (int)riders.size(); i++) {
+        if (riders[i].getPhoneNumber() == phone) {
+            return i;
+        }
+    }
+    return -1;
+}
+
+int findDriverIndexByPhone(const std::vector<Driver> &drivers, const std::string &phone) {
+    for (int i = 0; i < (int)drivers.size(); i++) {
+        if (drivers[i].getPhoneNumber() == phone) {
+            return i;
+        }
+    }
+    return -1;
+}
+
+std::string autoAAn(const std::string &word) {
+    if (word.empty()) return "";
+    if (word[0] == 'A' || word[0] == 'E' || word[0] == 'I' || word[0] == 'O' || word[0] == 'U') {
+        return "an";
+    }
+    return "a";
+}
+
+int main(int argc, char *argv[]) {
+    //take 3 arguments
+    if (argc < 8) {
+        std::cout << "Usage: nyride drivers.txt riders.txt output0.txt output1.txt output2.txt phoneNumber [request|cancel]\n" << std::endl;
+        return 1;
+    }
+    //load arguments
+    const std::string drivers_fName = argv[1];
+    const std::string riders_fName = argv[2];
+    std::string msg_fName = argv[3];
+    std::string updated_drivers_fName = argv[4];
+    std::string updated_riders_fName = argv[5];
+    std::string phone_number = argv[6];
+    std::string command = argv[7];
+    //turn on debug mode is last argument is debug
+    bool debug_mode = false;
+    if (std::string(argv[argc - 1]) == "debug") {
+        debug_mode = true;
+    }
+
+    if (debug_mode) {
+        debug_print("drivers_fName = " + drivers_fName);
+        debug_print("riders_fName = " + riders_fName);
+        debug_print("msg_fName = " + msg_fName);
+        debug_print("updated_drivers_fName = " + updated_drivers_fName);
+        debug_print("updated_riders_fName = " + updated_riders_fName);
+        debug_print("phone_number = " + phone_number);
+        debug_print("command = " + command);
+    }
+    //load drivers
+    std::vector<Driver> drivers;
+    std::ifstream drivers_file = loadFile(drivers_fName);
+    loadDrivers(drivers_file, drivers);
+    //load riders
+    std::vector<Rider> riders;
+    std::ifstream riders_file = loadFile(riders_fName);
+    loadRiders(riders_file, riders);
+    if (debug_mode) {
+        debug_print("drivers.size() = " + std::to_string(drivers.size()));
+        debug_print("riders.size() = " + std::to_string(riders.size()));
+    }
+    //check if phone number is valid
+    std::ostringstream msg;
+    if (!isPhoneNumberValid(phone_number)) {
+        std::cout << "Error: Invalid phone number" << std::endl;
+        msg << "Phone number is invalid.\n";
+        saveFile(msg_fName, msg.str());
+        return 1;
+    }
+    //check if command is valid
+    if (command != "request" && command != "cancel") {
+        std::cout << "Error: Invalid command" << std::endl;
+        return 1;
+    } else if (command == "request") {
+        //for request cases
+        int rIdx = findRiderIndexByPhone(riders, phone_number);
+        if (rIdx == -1) {
+            //if rider does not exist
+            msg << "Account does not exist.\n";
+            saveFile(msg_fName, msg.str());
+            return 1;
+        }
+        Rider &r = riders[rIdx];
+        //check rider
+        if (r.getCurrentState() == "Driver_on_the_way") {
+            msg << "You have already requested a ride and your driver is on the way to the pickup location.\n";
+            saveFile(msg_fName, msg.str());
+            return 1;
+        }
+        if (r.getCurrentState() == "During_the_trip") {
+            msg << "You can not request a ride at this moment as you are already on a trip.\n";
+            saveFile(msg_fName, msg.str());
+            return 1;
+        }
+        if (r.getCurrentState() == "Ready_to_request") {
+            msg << "Ride requested for rider " << r.getFirstName()
+                << ", looking for " << autoAAn(r.getVehiclePref()) << " "
+                << r.getVehiclePref() << " vehicle.\n"
+                << "Pick Up Location: " << r.getPickupLocationName()
+                << ", Drop Off Location: " << r.getDropoffLocationName() << ".\n";
+            //find closest driver
+            int dIdx = findClosestDriver(drivers, r);
+            if (dIdx == -1) {
+                //no driver
+                msg << "Sorry we can not find a driver for you at this moment.\n";
+            } else {
+                Driver &d = drivers[dIdx];
+                double dist = calculateDistance(d.getLatitude(), d.getLongitude(),
+                                                r.getPickupLatitude(), r.getPickupLongitude());
+                dist = (int)(dist * 10) / 10.0; //cut to 1 decimal
+                msg << "We have found the closest driver " << d.getFirstName() << "("
+                    << std::fixed << std::setprecision(1) << d.getRating() << ") for you.\n"
+                    << d.getFirstName() << " is now " 
+                    << std::fixed << std::setprecision(1) << dist 
+                    << " miles away from you.\n";
+                //update status
+                d.setCurrentState("On_the_way_to_pickup");
+                d.setRiderInfo(r.getFirstName(), r.getLastName(), r.getPhoneNumber());
+                r.setCurrentState("Driver_on_the_way");
+                r.setDriverInfo(d.getFirstName(), d.getLastName(), d.getPhoneNumber());
+            }
+        }
+    } else if (command == "cancel") {
+        //for cancel cases
+        //find phone_number in riders
+        int rIdx = findRiderIndexByPhone(riders, phone_number);
+        if (rIdx == -1) {
+            //in case of driver's cancel
+            int dIdx = findDriverIndexByPhone(drivers, phone_number);
+            if (dIdx == -1) {
+                //in case of not both rider and driver
+                msg << "Account does not exist.\n";
+                saveFile(msg_fName, msg.str());
+                return 1;
+            }
+            Driver &driver = drivers[dIdx];
+            if (driver.getCurrentState() != "On_the_way_to_pickup") {
+                msg << "You can only cancel a ride request if you are currently on the way to the pickup location.\n";
+                saveFile(msg_fName, msg.str());
+                return 1;
+            }
+            //get rider's phone number
+            std::string rPh = driver.getRiderPhoneNumber();
+            //clean driver's rider info
+            driver.setCurrentState("Available");
+            driver.setRiderInfo("", "", "");
+            msg << "Your driver " << driver.getFirstName()
+                << " has canceled the ride request. We will now find a new driver for you.\n";
+            //find rider
+            int theRiderIdx = findRiderIndexByPhone(riders, rPh);
+            Rider &r = riders[theRiderIdx];
+            //reset rider
+            r.setCurrentState("Ready_to_request");
+            r.setDriverInfo("", "", "");
+            //find a new driver
+            msg << "Ride requested for rider " << r.getFirstName()
+                << ", looking for " << autoAAn(r.getVehiclePref()) << " "
+                << r.getVehiclePref() << " vehicle.\n"
+                << "Pick Up Location: " << r.getPickupLocationName()
+                << ", Drop Off Location: " << r.getDropoffLocationName() << ".\n";
+            int newDIdx = findClosestDriver(drivers, r);
+            if (newDIdx == -1) {
+                msg << "Sorry we can not find a driver for you at this moment.\n";
+            } else {
+                Driver &newDriver = drivers[newDIdx];
+                double dist = calculateDistance(newDriver.getLatitude(), newDriver.getLongitude(),
+                                                r.getPickupLatitude(), r.getPickupLongitude());
+                dist = (int)(dist * 10) / 10.0; //cut to 1 decimal
+                msg << "We have found the closest driver " << newDriver.getFirstName() << "("
+                    << std::fixed << std::setprecision(1) << newDriver.getRating() << ") for you.\n"
+                    << newDriver.getFirstName() << " is now " 
+                    << std::fixed << std::setprecision(1) << dist 
+                    << " miles away from you.\n";
+                //update driver's status
+                newDriver.setCurrentState("On_the_way_to_pickup");
+                newDriver.setRiderInfo(r.getFirstName(), r.getLastName(), r.getPhoneNumber());
+                //update rider's status
+                r.setCurrentState("Driver_on_the_way");
+                r.setDriverInfo(newDriver.getFirstName(), newDriver.getLastName(), newDriver.getPhoneNumber());
+            }
+        } else {
+            //in case of rider's cancel
+            Rider &rider = riders[rIdx];
+            if (rider.getCurrentState() != "Driver_on_the_way") {
+                msg << "You can only cancel a ride request if your driver is currently on the way to the pickup location.\n";
+                saveFile(msg_fName, msg.str());
+                return 1;
+            }
+            //find driver's phone_number
+            std::string dPh = rider.getDriverPhoneNumber();
+            msg << "Ride request for rider " << rider.getFirstName()
+                << " is now canceled by the rider.\n";
+            //set driver's status to Available
+            int dIdx = findDriverIndexByPhone(drivers, dPh);
+            if (dIdx != -1) {
+                Driver &drv = drivers[dIdx];
+                drv.setCurrentState("Available");
+                drv.setRiderInfo("", "", "");
+            }
+            //set rider's status to Ready_to_request
+            rider.setCurrentState("Ready_to_request");
+            rider.setDriverInfo("", "", "");
+        }
+    }
+    //save msg
+    saveFile(msg_fName, msg.str());
+    //save updated drivers and riders
+    exportDrivers(updated_drivers_fName, drivers);
+    exportRiders(updated_riders_fName, riders);
+
+    return 0;
+}
\ No newline at end of file
diff --git a/hws/spotify_playlists/nyplaylists.cpp b/hws/spotify_playlists/nyplaylists.cpp
index e190ffa..a14ce77 100644
--- a/hws/spotify_playlists/nyplaylists.cpp
+++ b/hws/spotify_playlists/nyplaylists.cpp
@@ -1,5 +1,5 @@
 //An implement of CSCI-1200 HW1 Spotify Playlists
-//Author: Jinshan ZHou
+//Author: Jinshan Zhou
 //Date: 2025/1/16
 #include <vector>
 #include <string>
diff --git a/hws/spotify_playlists/output.txt b/hws/spotify_playlists/output.txt
deleted file mode 100644
index 79d0b29..0000000
--- a/hws/spotify_playlists/output.txt
+++ /dev/null
@@ -1,18 +0,0 @@
-"Someone Like You" Adele
-"Shallow" Lady Gaga, Bradley Cooper
-"Happier" Marshmello
-"Blinding Lights" The Weeknd
-"Levitating" Dua Lipa
-"Uptown Funk" Mark Ronson, Bruno Mars
-"Imagine" John Lennon
-"Bad Romance" Lady Gaga current
-"Hotel California" Eagles
-"Bohemian Rhapsody" Queen
-"Stairway to Heaven" Led Zeppelin
-"Smells Like Teen Spirit" Nirvana
-"Like a Rolling Stone" Bob Dylan
-"Hey Jude" The Beatles
-"Perfect" Ed Sheeran
-"Rolling in the Deep" Adele
-"Bad Guy" Billie Eilish
-"Dance Monkey" Tones and I