A rectangular polygon is a polygon whose edges are all parallel to the coordinate axes. The polygon must have a single, non-intersecting boundary.
You are given several horizontal line segments. You may remove some of the given segments and add any number of vertical segments to construct a rectangular polygon. Your goal is to maximize the number of edges in the final polygon.
You will be given ints x1, x2, and y. (x1[i], y[i]) and (x2[i], y[i]) are the end points of the i-th line segment. The given segments will have no common points. Return the maximal number of edges in a polygon that can be constructed using the above method. If no polygon can be constructed, return 0.