Add 2026.07.01 homework

notes-and-examples/2026.07.01/overview.md

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+## Outline
+
+- Review tree rotations and red-black trees
+- Properties of a red-black tree
+    - Top (root) node is black
+    - The children and parent of a red node are black
+    - Null nodes are colored black
+    - The path from any particular node to a null node must contain the
+      same number of black nodes
+- Dive into the steps for rebalancing a red-black tree
+
+Also see the accompanying whiteboard pictures.
+
+![Rotations](rotations.png)
+
+![Red-black trees](red-black-trees.png)
+
+## Assignment
+
+**Clarifications on the red-black tree example:**
+
+- In your assignment, you should first color a node _red_ when inserting it.
+    - Then, check for red-red violations (the second rule). Then, rebalance if necessary.
+- If the uncle of the inserted node (parent → parent → right child) is red,
+  you'll want to do two things:
+    - Color the parent, uncle, and grandparent in a way which preserves all the rules
+      (which ones are colored which, are an exercise left to you)
+    - _Recursively_ run the rebalancing algorithm on the grandparent
+- Otherwise, your task is to figure out the correct conditions in which
+  each of the rebalancing algorithms apply.
+
+Copy 2026.07.01/homework.py into your own [Git repository](https://gitea.bchen.dev/ethan/dsa-homework),
+with a new folder for the date. Implement the `rebalance_from_just_inserted`
+function.
+
+Don't change the test cases, but use them to inform how you implement your
+code. Try to pass all the test cases.
+
+Follow the instructions from last session (2026.06.12) to commit and push
+your changes to Gitea.
+