0757. Set Intersection Size At Least Two

https://leetcode.com/problems/set-intersection-size-at-least-two

Description

An integer interval [a, b] (for integers a < b) is a set of all consecutive integers from a to b, including a and b.

Find the minimum size of a set S such that for every integer interval A in intervals, the intersection of S with A has a size of at least two.

Example 1:

**Input:** intervals = [[1,3],[1,4],[2,5],[3,5]]
**Output:** 3
**Explanation:** Consider the set S = {2, 3, 4}.  For each interval, there are at least 2 elements from S in the interval.
Also, there isn't a smaller size set that fulfills the above condition.
Thus, we output the size of this set, which is 3.

Example 2:

**Input:** intervals = [[1,2],[2,3],[2,4],[4,5]]
**Output:** 5
**Explanation:** An example of a minimum sized set is {1, 2, 3, 4, 5}.

Constraints:

• 1 <= intervals.length <= 3000

• intervals[i].length == 2

• 0 <= ai < bi <= 108

ac