1396.设计地铁系统.java

/*
 * @lc app=leetcode.cn id=1396 lang=java
 *
 * [1396] 设计地铁系统
 *
 * https://leetcode.cn/problems/design-underground-system/description/
 *
 * algorithms
 * Medium (42.26%)
 * Likes:    97
 * Dislikes: 0
 * Total Accepted:    22.8K
 * Total Submissions: 54K
 * Testcase Example:  '["UndergroundSystem","checkIn","checkIn","checkIn","checkOut","checkOut","checkOut","getAverageTime","getAverageTime","checkIn","getAverageTime","checkOut","getAverageTime"]\n' +
  '[[],[45,"Leyton",3],[32,"Paradise",8],[27,"Leyton",10],[45,"Waterloo",15],[27,"Waterloo",20],[32,"Cambridge",22],["Paradise","Cambridge"],["Leyton","Waterloo"],[10,"Leyton",24],["Leyton","Waterloo"],[10,"Waterloo",38],["Leyton","Waterloo"]]'
 *
 * 地铁系统跟踪不同车站之间的乘客出行时间，并使用这一数据来计算从一站到另一站的平均时间。
 * 
 * 实现 UndergroundSystem 类：
 * 
 * 
 * void checkIn(int id, string stationName, int t)
 * 
 * 
 * 通行卡 ID 等于 id 的乘客，在时间 t ，从 stationName 站进入
 * 乘客一次只能从一个站进入
 * 
 * 
 * void checkOut(int id, string stationName, int t)
 * 
 * 通行卡 ID 等于 id 的乘客，在时间 t ，从 stationName 站离开
 * 
 * 
 * double getAverageTime(string startStation, string endStation)
 * 
 * 返回从 startStation 站到 endStation 站的平均时间
 * 平均时间会根据截至目前所有从 startStation 站 直接 到达 endStation 站的行程进行计算，也就是从 startStation
 * 站进入并从 endStation 离开的行程
 * 从 startStation 到 endStation 的行程时间与从 endStation 到 startStation
 * 的行程时间可能不同
 * 在调用 getAverageTime 之前，至少有一名乘客从 startStation 站到达 endStation 站
 * 
 * 
 * 
 * 
 * 你可以假设对 checkIn 和 checkOut 方法的所有调用都是符合逻辑的。如果一名乘客在时间 t1 进站、时间 t2 出站，那么 t1 < t2
 * 。所有时间都按时间顺序发生。
 * 
 * 
 * 示例 1：
 * 
 * 
 * 输入
 * 
 * ["UndergroundSystem","checkIn","checkIn","checkIn","checkOut","checkOut","checkOut","getAverageTime","getAverageTime","checkIn","getAverageTime","checkOut","getAverageTime"]
 * 
 * [[],[45,"Leyton",3],[32,"Paradise",8],[27,"Leyton",10],[45,"Waterloo",15],[27,"Waterloo",20],[32,"Cambridge",22],["Paradise","Cambridge"],["Leyton","Waterloo"],[10,"Leyton",24],["Leyton","Waterloo"],[10,"Waterloo",38],["Leyton","Waterloo"]]
 * 
 * 输出
 * 
 * [null,null,null,null,null,null,null,14.00000,11.00000,null,11.00000,null,12.00000]
 * 
 * 解释
 * UndergroundSystem undergroundSystem = new UndergroundSystem();
 * undergroundSystem.checkIn(45, "Leyton", 3);
 * undergroundSystem.checkIn(32, "Paradise", 8);
 * undergroundSystem.checkIn(27, "Leyton", 10);
 * undergroundSystem.checkOut(45, "Waterloo", 15);  // 乘客 45 "Leyton" ->
 * "Waterloo" ，用时 15-3 = 12
 * undergroundSystem.checkOut(27, "Waterloo", 20);  // 乘客 27 "Leyton" ->
 * "Waterloo" ，用时 20-10 = 10
 * undergroundSystem.checkOut(32, "Cambridge", 22); // 乘客 32 "Paradise" ->
 * "Cambridge" ，用时 22-8 = 14
 * undergroundSystem.getAverageTime("Paradise", "Cambridge"); // 返回 14.00000
 * 。只有一个 "Paradise" -> "Cambridge" 的行程，(14) / 1 = 14
 * undergroundSystem.getAverageTime("Leyton", "Waterloo");    // 返回 11.00000
 * 。有两个 "Leyton" -> "Waterloo" 的行程，(10 + 12) / 2 = 11
 * undergroundSystem.checkIn(10, "Leyton", 24);
 * undergroundSystem.getAverageTime("Leyton", "Waterloo");    // 返回 11.00000
 * undergroundSystem.checkOut(10, "Waterloo", 38);  // 乘客 10 "Leyton" ->
 * "Waterloo" ，用时 38-24 = 14
 * undergroundSystem.getAverageTime("Leyton", "Waterloo");    // 返回 12.00000
 * 。有三个 "Leyton" -> "Waterloo" 的行程，(10 + 12 + 14) / 3 = 12
 * 
 * 
 * 示例 2：
 * 
 * 
 * 输入
 * 
 * ["UndergroundSystem","checkIn","checkOut","getAverageTime","checkIn","checkOut","getAverageTime","checkIn","checkOut","getAverageTime"]
 * 
 * [[],[10,"Leyton",3],[10,"Paradise",8],["Leyton","Paradise"],[5,"Leyton",10],[5,"Paradise",16],["Leyton","Paradise"],[2,"Leyton",21],[2,"Paradise",30],["Leyton","Paradise"]]
 * 
 * 输出
 * [null,null,null,5.00000,null,null,5.50000,null,null,6.66667]
 * 
 * 解释
 * UndergroundSystem undergroundSystem = new UndergroundSystem();
 * undergroundSystem.checkIn(10, "Leyton", 3);
 * undergroundSystem.checkOut(10, "Paradise", 8); // 乘客 10 "Leyton" ->
 * "Paradise" ，用时 8-3 = 5
 * undergroundSystem.getAverageTime("Leyton", "Paradise"); // 返回 5.00000 ，(5) /
 * 1 = 5
 * undergroundSystem.checkIn(5, "Leyton", 10);
 * undergroundSystem.checkOut(5, "Paradise", 16); // 乘客 5 "Leyton" ->
 * "Paradise" ，用时 16-10 = 6
 * undergroundSystem.getAverageTime("Leyton", "Paradise"); // 返回 5.50000 ，(5 +
 * 6) / 2 = 5.5
 * undergroundSystem.checkIn(2, "Leyton", 21);
 * undergroundSystem.checkOut(2, "Paradise", 30); // 乘客 2 "Leyton" ->
 * "Paradise" ，用时 30-21 = 9
 * undergroundSystem.getAverageTime("Leyton", "Paradise"); // 返回 6.66667 ，(5 +
 * 6 + 9) / 3 = 6.66667
 * 
 * 
 * 
 * 
 * 提示：
 * 
 * 
 * 1 <= id, t <= 10^6
 * 1 <= stationName.length, startStation.length, endStation.length <= 10 次
 * 所有字符串由大小写英文字母与数字组成
 * 总共最多调用 checkIn、checkOut 和 getAverageTime 方法 2 * 10^4 
 * 与标准答案误差在 10^-5 以内的结果都被视为正确结果
 * 
 * 
 */

// @lc code=start

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.atomic.AtomicInteger;

class CheckRecord {
    // 站点名称
    private String stationName;

    // 时间
    private int time;

    public CheckRecord(String stationName, int time) {
        this.stationName = stationName;
        this.time = time;
    }

    public String getStationName() {
        return this.stationName;
    }

    public int getTime() {
        return this.time;
    }
}

class Travel {
    // 出发站
    private String startStation;

    // 到达站
    private String endStation;

    public Travel(String startStation, String endStation) {
        this.startStation = startStation;
        this.endStation = endStation;
    }

    public String getStartStation() {
        return this.startStation;
    }

    public String getEndStation() {
        return this.endStation;
    }

    @Override
    public int hashCode() {
        return (this.startStation + "->" + this.endStation).hashCode();
    }

    @Override
    public boolean equals(Object obj) {
        if (obj instanceof Travel) {
            Travel travel = (Travel) obj;
            return this.startStation.equals(travel.startStation) && this.endStation.equals(travel.endStation);
        }

        return false;
    }
}

class Accumulator {
    // 总次数
    private AtomicInteger count;

    // 总时间
    private AtomicInteger totalTime;

    public Accumulator() {
        this.count = new AtomicInteger(0);
        this.totalTime = new AtomicInteger(0);
    }

    public void record(int time) {
        if (time < 0)
            throw new IllegalArgumentException("time must be positive");

        this.count.incrementAndGet();
        this.totalTime.addAndGet(time);
    }

    public double getAverageTime() {
        return this.totalTime.get() * 1.0 / this.count.get();
    }
}

class UndergroundSystem {
    private Map<Integer, CheckRecord> checkInMap;
    private Map<Travel, Accumulator> statistics;

    public UndergroundSystem() {
        this.checkInMap = new HashMap<>();
        this.statistics = new HashMap<>();
    }

    public void checkIn(int id, String stationName, int t) {
        checkInMap.put(id, new CheckRecord(stationName, t));
    }

    public void checkOut(int id, String stationName, int t) {
        CheckRecord checkInRecord = checkInMap.get(id);
        if (checkInRecord == null)
            throw new IllegalArgumentException("id not found");

        Travel travel = new Travel(checkInRecord.getStationName(), stationName);
        Accumulator accumulator = statistics.get(travel);
        if (accumulator == null) {
            accumulator = new Accumulator();
            statistics.put(travel, accumulator);
        }

        accumulator.record(t - checkInRecord.getTime());

        // 移除 checkIn 记录
        checkInMap.remove(id);
    }

    public double getAverageTime(String startStation, String endStation) {
        Travel travel = new Travel(startStation, endStation);
        Accumulator accumulator = statistics.get(travel);
        if (accumulator == null)
            return 0;

        return accumulator.getAverageTime();
    }
}

/**
 * Your UndergroundSystem object will be instantiated and called as such:
 * UndergroundSystem obj = new UndergroundSystem();
 * obj.checkIn(id,stationName,t);
 * obj.checkOut(id,stationName,t);
 * double param_3 = obj.getAverageTime(startStation,endStation);
 */
// @lc code=end