836. Rectangle Overlap
Description
Intuition
1D
For example, we have 2 segemnts (x1, x2), (x3, x4):
# case 1
x1              x2
|               |
-----------------
          x3              x4
          |               |
          -----------------
# case 2
x1              x2
|               |
-----------------
          x3              x4
          |               |
          -----------------
x1 < x4 && x3 < x2
2D
For 2d,
- horizontal- must satisfy x1 < x4 && x3 < x2
 
- must satisfy 
- Vertical- must satisfy y1 < y4 && y3 < y2
 
- must satisfy