problem_200.js

// This problem was asked by Microsoft.
//
// Let `X` be a set of n intervals on the real line. We say that a set of points `P` "stabs" `X` if every interval in `X` contains at least one point in `P`. Compute the smallest set of points that stabs `X`.
//
// For example, given the intervals `[(1, 4), (4, 5), (7, 9), (9, 12)]`, you should return `[4, 9]`.