Merge pull request #8 from Signez/rust

Add a simple Rust version to the mix

Author: Tristramg

.gitignore

@@ -4,3 +4,5 @@ csa_hs
 csa_cpp
 csa_go
 *.class
+target/
+Cargo.lock

Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "csa_rs"
+version = "0.1.0"
+authors = ["Stanislas Signoud <[email protected]>"]
+
+[[bin]]
+name = "csa_rs"
+path = "csa.rs"
+

csa.rs

@@ -0,0 +1,125 @@
+use std::io;
+use std::iter::repeat;
+
+const MAX_STATIONS: usize = 100000;
+
+#[derive(Debug)]
+struct Connection {
+    departure_station: usize,
+    arrival_station: usize,
+    departure_timestamp: u32,
+    arrival_timestamp: u32
+}
+
+impl Connection {
+    fn parse(line: &str) -> Connection {
+        let mut splitted = line.split(" ").map(|bite| { bite.parse::<u32>().unwrap() });
+
+        Connection {
+            departure_station: splitted.next().unwrap() as usize,
+            arrival_station: splitted.next().unwrap() as usize,
+            departure_timestamp: splitted.next().unwrap(),
+            arrival_timestamp: splitted.next().unwrap(),
+        }
+    }
+}
+
+fn csa_main_loop(timetable: &[Connection], arrival_station: usize, earliest_arrival: &mut [u32], in_connection: &mut [usize]) {
+    let mut earliest = std::u32::MAX;
+
+    for (i, connection) in timetable.iter().enumerate() {
+        if connection.departure_timestamp >= earliest_arrival[connection.departure_station] &&
+                connection.arrival_timestamp < earliest_arrival[connection.arrival_station] {
+            earliest_arrival[connection.arrival_station] = connection.arrival_timestamp;
+            in_connection[connection.arrival_station] = i;
+
+            if connection.arrival_station == arrival_station && connection.arrival_timestamp < earliest {
+                earliest = connection.arrival_timestamp;
+            }
+        } else if connection.arrival_timestamp > earliest {
+            break;
+        }
+    }
+}
+
+fn csa_print_result(timetable: &Vec<Connection>, in_connection: &[usize], arrival_station: usize) {
+    if in_connection[arrival_station] == std::u32::MAX as usize {
+        println!("NO_SOLUTION");
+    } else {
+        let mut route = Vec::new();
+        let mut last_connection_index = in_connection[arrival_station];
+
+        while last_connection_index != std::u32::MAX as usize {
+            let ref connection = timetable[last_connection_index];
+            route.push(connection);
+            last_connection_index = in_connection[connection.departure_station];
+        }
+
+        for connection in route.iter().rev() {
+            println!("{} {} {} {}", connection.departure_station, connection.arrival_station, connection.departure_timestamp, connection.arrival_timestamp);
+        }
+    }
+    println!("");
+}
+
+fn csa_compute(timetable: &Vec<Connection>, departure_station: usize, arrival_station: usize, departure_time: u32)
+{
+    let mut in_connection = Vec::new();
+    in_connection.extend(repeat(std::u32::MAX as usize).take(MAX_STATIONS));
+    let mut earliest_arrival = Vec::new();
+    earliest_arrival.extend(repeat(std::u32::MAX).take(MAX_STATIONS));
+
+    earliest_arrival[departure_station as usize] = departure_time;
+
+    if departure_station < MAX_STATIONS && arrival_station < MAX_STATIONS {
+        csa_main_loop(&timetable, arrival_station, &mut earliest_arrival, &mut in_connection);
+    }
+
+    csa_print_result(&timetable, &in_connection, arrival_station);
+}
+
+fn main() {
+    let mut timetable = Vec::<Connection>::new();
+
+    // Importing connections
+
+    loop {
+        let raw_line = {
+            let mut line = String::new();
+            io::stdin().read_line(&mut line).ok().expect("failed to read connection line");
+            line
+        };
+        let input_line = raw_line.trim_right();
+
+        if input_line.is_empty() {
+            break;
+        } else {
+            timetable.push(Connection::parse(input_line));
+        };
+    }
+
+    // Responding to requests from stdin
+
+    loop {
+        let raw_line = {
+            let mut line = String::new();
+            io::stdin().read_line(&mut line).ok().expect("failed to read connection line");
+            line
+        };
+        let input_line = raw_line.trim_right();
+
+        if input_line.is_empty() {
+            break;
+        } else {
+            let params = input_line.split(" ")
+                .map(|bite| { bite.parse().ok().expect(&format!("failed to read {} as integer", bite)) })
+                .collect::<Vec<u32>>();
+
+            let departure_station = params[0] as usize;
+            let arrival_station = params[1] as usize;
+            let departure_time = params[2];
+
+            csa_compute(&timetable, departure_station, arrival_station, departure_time);
+        }
+    }
+}

readme.md

@@ -129,6 +129,12 @@ Run the test with ```ruby test.rb "java CSA"```
 
 Run the test with ```ruby test.rb "luajit csa.lua"```
 
+## Rust implementation
+
+Build: ```cargo build --release```
+
+Run the test with ```ruby test.rb ./target/release/csa_rs```
+
 ## Challenge
 
 Try to write: