现有k个商品的库存为(n1, n2, n3, ....., nk) 有m个订单,每个订单中各商品个数为 order1 (n11, n21, n31, ...., nk1) order2 (n12, n22, n32, ..., nk2) ..... orderm(n1m, n2m, n3m, ...., nkm) 问:如何选取多个订单,能在不超过各商品库存容量的前提下,使得下单的商品个数最多?