1.
(a)
                 1
                / \  \
               2   3  5
                  /  /
                 4  6
                   /
                  7
                 /
                8

(b)
                1
              / \  \
             2   3  7
                /  /\ \
               4  5 6  8

element: 1 2 3 4 5 6 7 8
rank:    2 0 1 0 0 0 1 0

(c)
                  1
                / /\
               2 3  5
                /  / \
               4  6   8
                 /
                7

2.
(a)
adjacency list:
1:7,8,9
2:4,9
3:5,6,8
4:2,9
5:3
6:3
7:1
8:1,3,9
9:1,2,4,8

(b)
                9
             / / \ \
            1 2  4  8
           /         \
          7           3
                     / \
                    5   6

(c)
                1
               / \
              7   8
                 /  \ 
                3    9
               / \    \
              5   6    4
                        \
                         2