feat: support passing tree as value to insert

src/MAryTree.test.ts

@@ -1,4 +1,4 @@
-import { MAryTree, MAryTreeNode } from "./MAryTree";
+import { MAryTree } from "./MAryTree";
 
 describe('MAryTree', () => {
   it('creates tree with single node', () => {
@@ -268,4 +268,23 @@ describe('MAryTree', () => {
     expect(b).toEqual([ 'G', 'H' ]);
 
   });
+
+  it('can combine trees', () => {
+    const bt1 = new MAryTree(1);
+
+    const bt2 = new MAryTree(2);
+
+    bt2.insert(2, 4);
+    bt2.insert(2, 5);
+    bt2.insert(5, 7);
+
+    bt1.insert(1, 2, bt2);
+
+    bt1.insert(1, 3);
+    bt1.insert(3, 6);
+
+    const a = Array.from(bt1.breadthFirstTraversal()).map(n => n.key);
+
+    expect(a).toEqual([ 1, 2, 3, 4, 5, 6, 7]);
+  });
 });

src/MAryTree.ts

@@ -345,7 +345,7 @@ export class MAryTree<K = MAryTreeKey, T = MAryTreeValue> {
   insert(
     parentNodeKey: K,
     key: K,
-    value?: T,
+    value?: T | MAryTree<K, T>,
   ): MAryTreeNode<K, T> | null {
     const parent = this.find(parentNodeKey);
 
@@ -356,10 +356,21 @@ export class MAryTree<K = MAryTreeKey, T = MAryTreeValue> {
         throw new Error('Cannot insert child node: parent already has max children');
       }
 
-      const node = new MAryTreeNode<K, T>(key, value, parent);
+      let node : MAryTreeNode<K, T> | null = null;
 
-      parent.children.push(node);
+      if (value && 'root' in value) {
+        node = new MAryTreeNode<K, T>(key, value.root.value, parent);
 
+        for (const child of value.root.children) {
+          child.parent = node
+          node.children.push(child);
+        }
+      } else {
+        node = new MAryTreeNode<K, T>(key, value as T, parent);
+      }
+
+      parent.children.push(node);
+
       return node;
     }