feat: color edges in red-black tree

Signed-off-by: Matej Focko <mfocko@redhat.com>

ranked_tree.js

@@ -37,10 +37,12 @@ class RankedTree {
 
         edges.forEach((vertices) => {
             let [u, v] = vertices;
+            let diff = nodeDifference(v);
+
             result.push(
                 `\t"Node(${u.value})" -> "Node(${
                     v.value
-                })" [label="${nodeDifference(v)}"];\n`
+                })" [label="${diff}"${this.styleEdge(diff)}];\n`
             );
         });
 
@@ -176,4 +178,8 @@ class RankedTree {
     deleteRebalance(node, parent) {
         throw "not implemented!";
     }
+
+    styleEdge(rankDifference) {
+        return "";
+    }
 }

rbt.js

@@ -158,4 +158,16 @@ class RBTree extends RankedTree {
             }
         }
     }
+
+    styleEdge(rankDifference) {
+        switch (rankDifference) {
+            case 2:
+                return " penwidth=2";
+            case 0:
+                return ', color="red"';
+            case 1:
+            default:
+                return "";
+        }
+    }
 }