Share the joy
For example, we have intervals
[1,3]
[2,7]
[3,6]
[5,5]
[8,9]
If we give a number 3, it should return:
[1,3]
[2,7]
[3,6]
Solution 1, Linear solution
An obvious solution is to iterate all intervals. This takes O(n) time.
Solution 2, Range tree.
Maintain 2 BST for left and right bound.
Find the range for left bound and right bound, and do intersection
