So binary search, the phonebook example, binary search on the pieces of paper on the white board, why is that?
是二分查找,例如电话簿的例子,对其中的某一页进行二分查找,为什么呢?
We started off talking about binary search, and I suggested that this was a log algorithm which it is, which is really kind of nice.
我告诉了你们这是一个对,数级的算法,这是很棒的,我们来一起看看这个算法到底做了什么。
It is a declaration of absolute interdependency among the things that we understand in binary terms but that we take somehow one to be causative of the other when we think about them.
这是在宣布事物之间的绝对的相互性,我们能在二元关系上理解这些事,但是我们惯常于把一个是当成另一个的原因。
Happiness is not a binary either-or, zero-one-- either I'm happy or I'm unhappy.
幸福不是二进制的非此即彼,0或-,要么幸福要么不幸福。
OK. Binary search is perhaps the simplest of the divide and conquer algorithms, and what does that mean? It says, in order to solve a problem, cut it down to a smaller problem and try and solve that one.
好了,二分搜索也许是,最简单的分治算法,这意味着什么?,也就是说,为了解决一个问题,把它切割成小的问题,然后再来一个个解决。
All right? I don't care what's in there, but just assume that's my list. And just to remind you, on your handout, and there it is on the screen, I'm going to bring it back up, there's the little binary search algorithm.
好,我不管列表里是什么,就假定那是一个列表,要提醒你们的是,在你们的讲义上和屏幕上,有一个简单的二分查找算法。
And the third thing I need to decide is how do I combine? You know, point out to you in the binary search case, combination was trivial. The answer to the final search was just the answer all the way up.
第三个问题是我需要决定如何进行合并?,就你们所知的,在二分查找中所打印出来的,合并的过程是非常简单的,最后查询的结果,就是一路上来所以的结果。
OK. So, what do I want you to take away from this? This idea of binary search is going to be a really powerful tool. And it has this property again, of chopping things into pieces.
从这里学到些什么?二分查找的思想,是一个非常有用的工具,我重复一遍,把问题拆成几部分来解决,那事实上,这里的增长率是多少?
This was using something called a bisection method, which is related to something called binary search, which we'll see lots more of later, to find square roots.
你应该想起来,我们是以一个,叫做二分法求平方根的问题结束的,它运用了二分法去求一个数的平方根,二分法和我们将要花很多时间。
In binary search-- ah, there's that wonderful phrase, this is called a version of binary search just like you saw bin-- or bi-section methods, - when we were doing numerical things- in binary search, I need to keep track of the starting point and the ending point of the list I'm looking at.
就是当我们处理数字的时候,所称的二分检索,在二分法搜索中,我需要记录区间的开始点和尾点,初始化的时候就是-,问题输入的开始点和尾点,当我开始做测试的时候,我想要做的就是去取中值点。
Remember, we saw that last time looking at the binary numbers. 2 to the n is a big number.
还记得吗,我们上次看过的二进制数,从2到n是一个很大的数。
On the other hand, watch what happens with binary. Is the partway one there?
噢,它只比100万的情况下多用了一步,请注意这就是?
The way in which we put signs together is to take these bundles, these binary relationships between a concept and a sound image, and adjust them in an unfolding sequence.
我们随意地将能指和所指捆在一起,也就是构成了一个事物和声音形象的关系,而且他们能被排列成话语。
Now, one of the questions we could still ask is, right, we've got binary search, which has got this nice log behavior.
目前,还有一个问题我们仍然要问的是,对,我们已经学了二分查找,有着非常好的log级别的行为。
And it's called divide and conquer for the obvious reason. I'm going to divide it up into sub-problems with the hope that those sub-problems get easier. It's going to be easier to conquer if you like, and then I'm going to merge them back. Now, in the binary search case, in some sense, this is a little bit trivial.
因此被称为分治的原因就这么简单,将一个问题分解成一些子问题,并希望这些子问题解决起来比较方便,正如你希望的,求解的过程也会变得简单,下面就是把结果合并起来,现在,在二分搜索的例子里,从某些方面来说,这有点微不足道。
to the n, every value in the 1 bit vector we looked at last time is either 0 or 1. So it's a binary n number of n bits, 2 to the n.
从2到n,我们上次看到的,位向量的每个值不是0就是,所以它是n,比特的二进制数,从2到。
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