So I haven't done magic, I've given you a really fast way to solve a knapsack problem, but it's still exponential deep down in its heart, in something.
所以我并没有施魔法,我已经告诉了你,一种快速解决背包问题的方法了,但是某些方面它的核心仍然是指数增长的。
Let's now go back and instantiate these ideas for the knapsack problem we looked at last time In particular, for the 0-1 knapsack problem.
让我们回来用具体例子,来说明我们上次看过的背包问题,特别是对0-1背包问题来说。
But let's look for a slight variant of it, where greedy is not so good. And that's what's called the zero-one knapsack problem.
但是让我们找一找它的一些变种,在这些变种中贪婪算法用处不大,这些问题也就是0/1背包问题。
So we'll start looking in detail at one problem, and that's the knapsack problem. Let's see.
让我们开始仔细讲讲一个问题,那就是背包问题。
with the continuous knapsack problem as we've formulated it, greedy is good.
因为正如我们已经归越过的,对于一般连续性背包问题贪婪算法很实用。
So let's look at an example of a zero-one knapsack problem.
我们要像之前一样将其最优化,现在让我们来看一个0/1背包问题的例子。
Typically up till now, we've looked at things that can be done in sublinear time. Or, at worst, polynomial time. We'll now look at a problem that does not fall into that. And we'll start with what's called the continuous knapsack problem.
至今为止我们已经处理过,亚线性问题,最多也就是多项式问题,我们现在要看的问题则是不能用这些解决的,我们将要开始讲连续背包问题。
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