special forms of binary trees there are few special forms of binary tree worth mentioning if every non-leaf node in binary tree has nonempty left and right subtreesthe tree is termed strictly binary tree orto put it another wayall of the nodes in strictly binary tree are of degree zero or twonever degree one strictly binary tree with leaves always contains nodes some texts call this "fullbinary tree complete binary tree of depth is the strictly binary tree all of whose leaves are at level the total number of nodes in complete binary tree of depth equals + since all leaves in such tree are at level dthe tree contains leaves andtherefore internal nodes diagram complete binary tree binary tree of depth is an almost complete binary tree ifeach leaf in the tree is either at level or at level for any node nd in the tree with right descendant at level dall the left descendants of nd that are leaves are also at level diagram an almost complete binary tree