tree
           |
          nr(0)
        /      \
     /            \
   n3(3)         n4(4)
  /             /    \
n1(1)         n5(5)  n2(2)
             /    \
          n6(6)  n7(7)
                /    \
             n8(8)   n9(9)
 tree2
   |
root(-1)
                    
         null
           |
     lonelyNode0(100)
     /
lonelyNode1(200)