已知
child parent
a b
a c
d b
d c
b e
b f
c g
c h
x g
x h
m x
m n
o x
o n
则
c 2+c+g 2+c+h 1+a+c 1+d+c
h 1+c+h 1+x+h
d 2+d+b 2+d+c
b 1+a+b 1+d+b 2+b+e 2+b+f
o 2+o+x 2+o+n
e 1+b+e
m 2+m+x 2+m+n
x 2+x+g 2+x+h 1+m+x 1+o+x
a 2+a+c 2+a+b
也即
gc[0] = a gc[1]=d
gp[0] = g gp[1] = h gc[0] = a gc[1]=d
gp[0] = e gp[1] = f gc[0] = m gc[1]=o
gp[0] = g gp[1] = h
则
grandchild grandparent
a g
a h
d g
d h
a e
a f
d e
d f
m g
m h
o g
o h