positions lists the (unsorted, distinct) spots along a corridor where a router may be mounted. You must
mount exactly m routers, each at a different spot, and you want the closest pair of routers to be as far
apart as possible. Return that largest achievable minimum distance.
Examples
Input: positions = [1, 2, 3, 4, 7], m = 3
Output: 3
Explanation: mount at 1, 4 and 7.
Input: positions = [5, 4, 3, 2, 1, 1000000000], m = 2
Output: 999999999
Input: positions = [1, 2, 3], m = 3
Output: 1
Constraints
2 <= m <= len(positions) <= 5 * 10**40 <= positions[i] <= 10**9, all distinct- Required time:
O(n log n + n log(max(positions))).
Goals
- Binary search over a distance and verify with a greedy placement
- Sort unsorted input before searching