# Divide & Conquer

## **Notes**

* Placeholder

## **Typical Questions**

* LC 21. Merge Two Sorted Lists
  * [Optimal Answer](https://leetcode.com/problems/merge-two-sorted-lists/submissions/1514180154). TC: $$O(m+n)$$, SC: $$O(1)$$
* LC 148. Sort List
  * Approach 1 with recursive merge sort: [Answer](https://leetcode.com/problems/sort-list/submissions/1868883937). TC: $$O(n\*logn)$$, SC: $$O(logn)$$
  * :thumbsup: :red\_circle: Approach 2 with iterative idea and SC O(1): <https://leetcode.com/problems/sort-list/solutions/46712/bottom-to-upnot-recurring-with-o1-space-anpva/comments/151523/>
* :white\_circle: LC 427. Construct Quad Tree&#x20;
  * [Optimal Answer](https://leetcode.com/problems/construct-quad-tree/submissions/1869668575).
  * TC: $$O(4^{log\_2{N}}) = O(N^{log\_24}) = O(N^2)$$&#x20;
  * SC: $$O(log\_2N)$$
* LC 108. Convert Sorted Array to Binary Search Tree
  * [Optimal Answer](https://leetcode.com/problems/convert-sorted-array-to-binary-search-tree/submissions/1738819172/). TC: $$O(n)$$, SC: $$O(log(n))$$