说明：  1.1 背包问题 有一个徒步旅行者，已知他能承受的旅行背包的重量不超过a（kg）。设有n种物品可供他选择装入背包，这n种物品分别编号为1，2，…，n。其中第i种物品每件的重量为ai（kg），其使用价值（指一件第i种物品对旅行者来说所带来的好处的一种数量指标）为ci（i＝1，2，…，n）。问这位旅行者应如何选择携带这n种物品的件数，使得总价值最大？
(1.1 knapsack problem is a hikers. he is known to travel to withstand the weight of the backpack not exceed a (kg). N Species with articles for his choice loaded backpack, n product were numbered 1, 2, ..., n. I first of which product each ai of the weight (kg), its value (i refers to a section of the types of items travelers the benefits brought by a number of indicators) for the ci (i = 1, 2, ..., n). Asked how travelers who choose to bring this product to the n pieces, making the total value of the largest?)