Conditions
- 1. root: XLB = YLB = -inf; XUB = YUB = inf
- 2. node N has node P as its parent and level(P) is even:
N.xlb = P.xlb if N = P.llink
N.xlb = P.xval if N = P.rlink
N.xub = P.xval if N = P.llink
N.xub = P.xub if N = P.rlink
N.ylb = P.ylb; N.yub = P.yub
- 3. node N has node P as its parent and level(P) is odd:
N.ylb = P.ylb if N = P.llink
N.ylb = P.yval if N = P.rlink
N.yub = P.yval if N = P.llink
N.yub = P.yub if N = P.rlink
N.xlb = P.xlb; N.xub = P.xub

slide: Bounds -- conditions