Let T be a rooted binary tree whose vertices are labelled with symbols a, b, c, d, e, f, g, h, i, j, k. Suppose the in-order and post-order traversals of T produce the following sequences.
in-order: a, b, c, d, e, f, g, h, i, j, k
post-order: a, c, b, e, f, h, j, k, i, g, d
How many leaves does the tree have?