🚴 perf(delete_one_child): Skip case 1 since n cannot be the root.

Author: make-github-pseudonymous-again

src/deletion/delete_one_child.js

@@ -5,20 +5,22 @@ import Node from '../types/Node.js';
 import Leaf from '../types/Leaf.js';
 
 import replace_node from './replace_node.js';
-import delete_case1 from './delete_case1.js';
+import delete_case2 from './delete_case2.js';
 
 /**
  * Delete a node <code>n</code> that has at most a single non-leaf child.
  *
  * Precondition:
  *   - n has at most one non-leaf child.
+ *   - n is not the root
  *   - if n has a non-leaf child, then it is its left child.
  *   - hence, n's right child is a leaf
  *
  * @param {Node} n - The node to delete.
  */
 const delete_one_child = (n) => {
 	assert(n instanceof Node);
+	assert(n.parent !== null);
 	// Precondition: n's right child is a leaf.
 	// The right child of n is always a LEAF because either n is a subtree
 	// predecessor or it is the only child of its parent by the red-black tree
@@ -39,7 +41,7 @@ const delete_one_child = (n) => {
 		if (child._color === RED) child._color = BLACK;
 		// Otherwise, there are more things to fix.
 		else {
-			delete_case1(child);
+			delete_case2(child);
 		}
 	} else {
 		//    If n is red then its child can only be black. Replacing n with its