Suppose we label the nodes of binomial tree Bk in binary by a postorder walk, as in Figure 19.4. Consider a node x labeled l at depth i, and let j = k - i. Show that x has j 1's in its binary representation. How many binary k-strings are there that contain exactly j 1's? Show that the degree of x is equal to the number of 1's to the right of the rightmost 0 in the binary representation of l.

这题就是算法导论第二版习题19.1-3. 感觉很难，一点头绪也没有，求助！！