Divide and Conquer

Two choices:

• We can blindly break the problem into smaller lists, sort them, then do some work to patch things up after the fact (like insertion sort).
• Or we can do some work up front so that when the subproblems are solved, we are left with a sorted list (like selection sort).

But we need to break our lists in half: T(n) = n + 2 T(n/2).

By balancing, we get $T(n) = n \log n$.