说明：  矩阵链乘： P=a1×a2×a3×……×an，依据乘法结合律，不改变其顺序，只用括号表示成对的乘积，试问有几种括号化的方案？(h(n)种) 出栈次序问题。
(Matrix chain multiplication: P=a1* A2* A3*......* an, according to the multiplication with law, does not change the order, the brackets only representation of the pairwise product, ask several brackets scheme? (H (n) species) 出栈次序问题。 Sequence problem. )