Mini Uber

本文主要是介绍Mini Uber，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

实现一个迷你优步

1. 司机提供他们的位置
2. 用户请求，然后返回一个匹配的司机

实现下列函数

• report(driver_id, lat, lng)
  • 如果没有找到匹配的trip，返回null
  • 否则返回匹配trip信息
• request(rider_id, lat, lng)
  1. 建立一个trip
  2. 找到一个最近的司机，标记这个司机为不可用
  3. 将司机id填入trip
  4. 返回trip

Java中trip的定义

public class Trip {public int id; // trip's id, primary keypublic int driver_id, rider_id; // foreign keypublic double lat, lng; // pick up location
}

思路：Integer to Trip,  Integer to Location，一个是用来返回已经有trip的driver， 一个是用来返回没有trip的driver，求最近就是求现有driver的跟rider的最小值；更新两个hashmap即可；如果找到了driver，就把他从没有trip的hashmap中去掉；

/*** Definition of Trip:* public class Trip {*     public int id; // trip's id, primary key*     public int driver_id, rider_id; // foreign key*     public double lat, lng; // pick up location*     public Trip(int rider_id, double lat, double lng);* }* Definition of Helper* class Helper {*     public static double get_distance(double lat1, double lng1,double lat2, double lng2) {*         // return distance between (lat1, lng1) and (lat2, lng2)*     }* };*/
public class MiniUber {private class Location {public double lat;public double lng;public Location(double lat, double lng) {this.lat = lat;this.lng = lng;}}private HashMap<Integer, Trip> driver2Trip;private HashMap<Integer, Location> driver2Location;public MiniUber() {driver2Trip = new HashMap<Integer, Trip>();driver2Location = new HashMap<Integer, Location>();}// @param driver_id an integer// @param lat, lng driver's location// return matched trip information if there have matched rider or nullpublic Trip report(int driver_id, double lat, double lng) {if(driver2Trip.containsKey(driver_id)) {return driver2Trip.get(driver_id);} else {// update location hashmap;if(driver2Location.containsKey(driver_id)) {driver2Location.get(driver_id).lat = lat;driver2Location.get(driver_id).lng = lng;} else {driver2Location.put(driver_id, new Location(lat, lng));}// return null trip info;return null;}}// @param rider_id an integer// @param lat, lng rider's location// return a trippublic Trip request(int rider_id, double lat, double lng) {Trip trip = new Trip(rider_id, lat, lng);double distance = -1;int driver_id = -1;for(Integer driver: driver2Location.keySet()) {Location location = driver2Location.get(driver);double dis = Helper.get_distance(lat, lng, location.lat, location.lng);if(distance == -1 || dis < distance) {distance = dis;driver_id = driver;}}if(driver_id != -1) {driver2Location.remove(driver_id);}trip.driver_id = driver_id;driver2Trip.put(driver_id, trip);return trip;}
}

 

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