Erect The Fence


@hell0123 The meaning of this line is that the line qr should be obtained by doing an anticlockwise rotation of the line pq, then only the point q can be more counterclockwise to p than r. For the line qr to be obtained by anitclockwise rotation of pq, qr's slope should be more than pq's slope.

@kevinchacon @hell0123 I have updated the statement. I hope the current explanation seems more logical.





@ykvarts We need hashset because of collinear points. Consider the case input contains only three collinear points. Then leftright scan and rightscan give the same result. Thanks.