Add solutions to bins

src/info_file.rs

@@ -49,6 +49,30 @@ impl ExerciseInfo {
 
         path
     }
+
+    /// Path to the solution file starting with the `solutions/` directory.
+    pub fn sol_path(&self) -> String {
+        let mut path = if let Some(dir) = &self.dir {
+            // 14 = 10 + 1 + 3
+            // solutions/ + / + .rs
+            let mut path = String::with_capacity(14 + dir.len() + self.name.len());
+            path.push_str("solutions/");
+            path.push_str(dir);
+            path.push('/');
+            path
+        } else {
+            // 13 = 10 + 3
+            // solutions/ + .rs
+            let mut path = String::with_capacity(13 + self.name.len());
+            path.push_str("solutions/");
+            path
+        };
+
+        path.push_str(&self.name);
+        path.push_str(".rs");
+
+        path
+    }
 }
 
 /// The deserialized `info.toml` file.