Leetcode Rust

Author: agSant01

leetcode/rust/.gitignore

@@ -0,0 +1,14 @@
+# Generated by Cargo
+# will have compiled files and executables
+debug/
+target/
+
+# Remove Cargo.lock from gitignore if creating an executable, leave it for libraries
+# More information here https://doc.rust-lang.org/cargo/guide/cargo-toml-vs-cargo-lock.html
+Cargo.lock
+
+# These are backup files generated by rustfmt
+**/*.rs.bk
+
+# MSVC Windows builds of rustc generate these, which store debugging information
+*.pdb

leetcode/rust/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "rust"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

leetcode/rust/src/_1396_design_underground_system.rs

@@ -0,0 +1,81 @@
+#![allow(unused)]
+
+use std::collections::HashMap;
+
+struct UndergroundSystem {
+    station_times: HashMap<(String, String), (f64, i32)>,
+    current_passengers: HashMap<i32, (String, i32)>,
+}
+
+/**
+ * `&self` means the method takes an immutable reference.
+ * If you need a mutable reference, change it to `&mut self` instead.
+ */
+impl UndergroundSystem {
+    fn new() -> Self {
+        return Self {
+            station_times: HashMap::new(),
+            current_passengers: HashMap::new(),
+        };
+    }
+
+    // O(1)
+    fn check_in(&mut self, id: i32, station_name: String, t: i32) {
+        self.current_passengers.insert(id, (station_name, t));
+    }
+
+    // O(1)
+    fn check_out(&mut self, id: i32, station_name: String, t: i32) {
+        if let Some((entry_station, entry_time)) = self.current_passengers.get(&id) {
+            let (ave_time, samples) = self
+                .station_times
+                .entry((entry_station.to_string(), station_name))
+                .or_default();
+
+            // Calculate rolling average
+
+            // prev_ave * samples
+            let curr_ave = *ave_time * (*samples as f64);
+            // increment samples
+            *samples += 1;
+
+            // new ave = ((Prev*Count) + NewVal) / (Count+1)
+            *ave_time = (curr_ave + (t - entry_time) as f64) / (*samples as f64);
+        }
+    }
+
+    // O(1)
+    fn get_average_time(&self, start_station: String, end_station: String) -> f64 {
+        if let Some((ave_time, _)) = self.station_times.get(&(start_station, end_station)) {
+            return *ave_time;
+        }
+        0.0
+    }
+}
+
+//  Your UndergroundSystem object will be instantiated and called as such:
+//  let obj = UndergroundSystem::new();
+//  obj.check_in(id, stationName, t);
+//  obj.check_out(id, stationName, t);
+//  let ret_3: f64 = obj.get_average_time(startStation, endStation);
+
+#[test]
+fn test1() {
+    let mut underground_system: UndergroundSystem = UndergroundSystem::new();
+    underground_system.check_in(10, String::from("Leyton"), 3);
+    underground_system.check_out(10, String::from("Paradise"), 8); // Customer 10 String::from("Leyton") -> String::from("Paradise") in 8-3 = 5
+
+    let r1 = underground_system.get_average_time(String::from("Leyton"), String::from("Paradise")); // return 5.00000, (5) / 1 = 5
+    assert_eq!(r1, 5.0);
+
+    underground_system.check_in(5, String::from("Leyton"), 10);
+    underground_system.check_out(5, String::from("Paradise"), 16); // Customer 5 String::from("Leyton") -> String::from("Paradise") in 16-10 = 6
+
+    let r2 = underground_system.get_average_time(String::from("Leyton"), String::from("Paradise")); // return 5.50000, (5 + 6) / 2 = 5.5
+    assert_eq!(r2, 5.5);
+
+    underground_system.check_in(2, String::from("Leyton"), 21);
+    underground_system.check_out(2, String::from("Paradise"), 30); // Customer 2 String::from("Leyton") -> String::from("Paradise") in 30-21 = 9
+    let r3 = underground_system.get_average_time(String::from("Leyton"), String::from("Paradise"));
+    assert_eq!(r3, 20.0 / 3.0); // return 6.66667, (5 + 6 + 9) / 3 = 6.66667
+}

leetcode/rust/src/main.rs

@@ -0,0 +1,5 @@
+mod _1396_design_underground_system;
+
+fn main() {
+    println!("Hello, world!");
+}