Implement the UndergroundSystem
class:
void checkIn(int id, string stationName, int t)
id
, gets in the station stationName
at time t
.void checkOut(int id, string stationName, int t)
id
, gets out from the station stationName
at time t
.double getAverageTime(string startStation, string endStation)
startStation
and the endStation
.startStation
to endStation
that happened directly.getAverageTime
is always valid.You can assume all calls to checkIn
and checkOut
methods are consistent. If a customer gets in at time t1 at some station, they get out at time t2 with t2 > t1. All events happen in chronological order.
Example 1:
Input ["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"]] Output [null,null,null,null,null,null,null,14.00000,11.00000,null,11.00000,null,12.00000] Explanation UndergroundSystem undergroundSystem = new UndergroundSystem(); undergroundSystem.checkIn(45, "Leyton", 3); undergroundSystem.checkIn(32, "Paradise", 8); undergroundSystem.checkIn(27, "Leyton", 10); undergroundSystem.checkOut(45, "Waterloo", 15); undergroundSystem.checkOut(27, "Waterloo", 20); undergroundSystem.checkOut(32, "Cambridge", 22); undergroundSystem.getAverageTime("Paradise", "Cambridge"); // return 14.00000. There was only one travel from "Paradise" (at time 8) to "Cambridge" (at time 22) undergroundSystem.getAverageTime("Leyton", "Waterloo"); // return 11.00000. There were two travels from "Leyton" to "Waterloo", a customer with id=45 from time=3 to time=15 and a customer with id=27 from time=10 to time=20. So the average time is ( (15-3) + (20-10) ) / 2 = 11.00000 undergroundSystem.checkIn(10, "Leyton", 24); undergroundSystem.getAverageTime("Leyton", "Waterloo"); // return 11.00000 undergroundSystem.checkOut(10, "Waterloo", 38); undergroundSystem.getAverageTime("Leyton", "Waterloo"); // return 12.00000
Example 2:
Input ["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"]] Output [null,null,null,5.00000,null,null,5.50000,null,null,6.66667] Explanation UndergroundSystem undergroundSystem = new UndergroundSystem(); undergroundSystem.checkIn(10, "Leyton", 3); undergroundSystem.checkOut(10, "Paradise", 8); undergroundSystem.getAverageTime("Leyton", "Paradise"); // return 5.00000 undergroundSystem.checkIn(5, "Leyton", 10); undergroundSystem.checkOut(5, "Paradise", 16); undergroundSystem.getAverageTime("Leyton", "Paradise"); // return 5.50000 undergroundSystem.checkIn(2, "Leyton", 21); undergroundSystem.checkOut(2, "Paradise", 30); undergroundSystem.getAverageTime("Leyton", "Paradise"); // return 6.66667
Constraints:
20000
operations.1 <= id, t <= 106
1 <= stationName.length <= 10
10-5
of the actual value will be accepted as correct.use std::collections::HashMap;
#[derive(Default)]
struct UndergroundSystem {
time: HashMap<String, HashMap<String, (i32, i32)>>,
customer: HashMap<i32, (String, i32)>,
}
impl UndergroundSystem {
fn new() -> Self {
UndergroundSystem::default()
}
fn check_in(&mut self, id: i32, start_station: String, start_t: i32) {
self.customer.insert(id, (start_station, start_t));
}
fn check_out(&mut self, id: i32, end_station: String, end_t: i32) {
let (start_station, start_t) = self.customer.remove(&id).expect("in");
let (sum, count) = self
.time
.entry(start_station)
.or_default()
.entry(end_station)
.or_default();
*sum += end_t - start_t;
*count += 1;
}
fn get_average_time(&mut self, start_station: String, end_station: String) -> f64 {
let (sum, count) = self
.time
.entry(start_station)
.or_default()
.entry(end_station)
.or_default();
*sum as f64 / *count as f64
}
}
#[test]
fn test() {
use assert_approx_eq::assert_approx_eq;
let mut obj = UndergroundSystem::new();
obj.check_in(45, "Leyton".to_string(), 3);
obj.check_in(32, "Paradise".to_string(), 8);
obj.check_in(27, "Leyton".to_string(), 10);
obj.check_out(45, "Waterloo".to_string(), 15);
obj.check_out(27, "Waterloo".to_string(), 20);
obj.check_out(32, "Cambridge".to_string(), 22);
let t = obj.get_average_time("Paradise".to_string(), "Cambridge".to_string());
assert_approx_eq!(t, 14.0);
let t = obj.get_average_time("Leyton".to_string(), "Waterloo".to_string());
assert_approx_eq!(t, 11.0);
obj.check_in(10, "Leyton".to_string(), 24);
let t = obj.get_average_time("Leyton".to_string(), "Waterloo".to_string());
assert_approx_eq!(t, 11.0);
obj.check_out(10, "Waterloo".to_string(), 38);
let t = obj.get_average_time("Leyton".to_string(), "Waterloo".to_string());
assert_approx_eq!(t, 12.0);
}