single threaded solution in bin

rust/src/bin/single_thread.rs

@@ -0,0 +1,56 @@
+use std::{
+    collections::HashMap,
+    fs::File,
+    io::{BufRead, BufReader},
+};
+
+struct StationMeasurements {
+    min: f64,
+    max: f64,
+    temps: Vec<f64>,
+}
+
+fn main() {
+    let mut stations: HashMap<String, StationMeasurements> = HashMap::new();
+
+    let file = File::open("../measurements.txt").expect("File measurements.txt not found");
+    let reader = BufReader::new(file);
+    let mut line_num = 0;
+    for line_result in reader.lines() {
+        line_num += 1;
+        if line_num % 50000 == 0 {
+            println!("Calculated {line_num} stations");
+        }
+        let line = line_result.expect("could not read line");
+        let (station, temp) = line.split_once(';').unwrap();
+        let temp = temp.parse().unwrap();
+        let measurements_option = stations.get_mut(station);
+        if let Some(measurements) = measurements_option {
+            if temp < measurements.min {
+                measurements.min = temp;
+            } else if temp > measurements.max {
+                measurements.max = temp;
+            }
+            measurements.temps.push(temp);
+        } else {
+            let measurements = StationMeasurements {
+                min: temp,
+                max: temp,
+                temps: vec![temp],
+            };
+            stations.insert(station.to_owned(), measurements);
+        }
+    }
+    for (station, measurments) in stations {
+        let min = measurments.min;
+        let max = measurments.max;
+        let avg = avg(measurments.temps);
+        println!("{station}={min}/{max}/{avg}");
+    }
+}
+
+fn avg(temps: Vec<f64>) -> f64 {
+    let num_temps = temps.len() as f64;
+    let sum_temps: f64 = temps.iter().sum();
+    sum_temps / num_temps
+}