dont use vectors

src/main.rs

@@ -5,7 +5,10 @@ use std::io::prelude::*;
 use std::collections::HashMap;
 
 struct Station {
-    values: Vec<f64>
+    min: f64,
+    max: f64,
+    sum: f64,
+    n: usize,
 }
 
 fn main() {
@@ -42,9 +45,17 @@ fn main() {
                 let name = String::from(&line[..n - i - 1]);
 
                 if let Some(station) = stations.get_mut(&name) {
-                    station.values.push(temp);
+                    station.min = station.min.min(temp);
+                    station.max = station.max.max(temp);
+                    station.sum += temp;
+                    station.n += 1;
                 } else {
-                    stations.insert(name, Station { values: vec![temp] });
+                    stations.insert(name, Station {
+                        min: temp,
+                        max: temp,
+                        sum: temp,
+                        n: 1,
+                    });
                 }
                 break;
             }
@@ -54,10 +65,11 @@ fn main() {
     let mut stations: Vec<_> = stations.iter().collect();
     stations.sort_unstable_by(|(n1, _), (n2, _)| n1.cmp(n2));
     for (name, station) in stations {
-        assert!(!station.values.is_empty());
-        println!("{};{:.1};{:.1};{:.1}", name,
-            station.values.iter().cloned().fold(100., f64::min),
-            station.values.iter().sum::<f64>() / station.values.len() as f64,
-            station.values.iter().cloned().fold(-100., f64::max))
+        println!("{};{:.1};{:.1};{:.1}",
+            name,
+            station.min,
+            station.sum / station.n as f64,
+            station.max
+        );
     }
 }