refactor: changed Display implementation

src/lib.rs

@@ -580,19 +580,30 @@ impl Mul for Matrix {
     }
 }
 
-impl Display for Matrix {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        let mut display = String::new();
-        let mut index = 0;
-        for _i in 0..self.columns {
-            display += "{";
-            for _k in 0..self.rows {
-                display += &format!(" {},", self.data[index]);
-                index += 1;
+impl fmt::Display for Matrix {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        let strings: Vec<String> = self.data.iter().map(|x| x.to_string()).collect();
+
+        let max_width = strings.iter().map(|s| s.len()).max().unwrap_or(0);
+
+        for r in 0..self.rows {
+            write!(f, "{{ ")?;
+
+            for c in 0..self.columns {
+                let idx = r * self.columns + c;
+                let val = &strings[idx];
+
+                write!(f, "{:>width$}", val, width = max_width)?;
+
+                if c != self.columns - 1 {
+                    write!(f, ", ")?;
+                }
             }
-            display += " }\n";
+
+            writeln!(f, " }}")?;
         }
-        write!(f, "{}", display)
+
+        Ok(())
     }
 }