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Let's do selection and let's do merge sort here on the right just to see what actually happens.
中间进行选择排序，右边进行归并排序,看看会发生什么。
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And this is in contrast to Selection Sort where you're fishing again and again for the then smallest element.
这与选择排序是相反的,在选择排序中你需要一次又一次地,找出最小的元素。
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How many swaps do I do in general in bubble sort, compared to selection source?
在冒泡排序中，一般要做多少次交换,对比选择排序呢？
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Just contrast this for a brief moment to something like Selection Sort which from the get go had a ridiculous amount of redundancy comparing the same damn numbers again and again, and again.
这就与其他的排序算法形成了鲜明的对比,比如选择排序,它会一次又一次地做,多余的比较。
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And in fact, if we count up all of these silly comparisons I was making verbally I bet I'm gonna be making fewer in the end than I was with bubble or with selection.
事实上，如果将所有的,比较次数加起来，我敢打赌,比起冒泡和选择排序,它最终的比较次数是相对较少的。
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And this was just a formal way of describing the best case running time and in the case of Selection Sort, what was the best case running time?
这是描述最好情况下运行时间的,一种正式的方式,在选择排序中，最理想的运行时间是多少呢？
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We looked at something called Selection Sort and that too was pretty straightforward, at least conceptually.
例如选择排序,至少从概念上来说，它非常简单。
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So Selection Sort, while it might be easier perhaps to think through than Bubble Sort, or maybe it's pretty much equivalent, it's just a different approach to the same problem.
因此，仔细想想，选择排序也许比,冒泡排序更简单，或者这两者都差不多，只是对同一问题的不同方法而已。
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Selection sort too really reduces to a total number of comparisons because I'm again comparing the current smallest to the next thing I see, the next thing, so really a lot of these sorting algorithms boil down to comparisons and the numbers that you actually have to make.
选择排序也可归纳为总数的比较,因为要将当前最小者与下一个进行比较,接着再下一个，可见,很多排序算法都可归结为比较,以及需要比较的次数。
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It blows selection and Bubble Sorts out of the water, but why is that?
它比选择和冒泡排序,更高效，为什么呢？
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I just go down the list selecting the smallest person at a time and then I repeat, repeat, repeat but when we actually did out the math or kind of reason through it, the running time, the asymptotic running time of bub-- of Selection Sort was also what?
只需要遍历列表，每次找出最小的元素,然后重复上述步骤，但从数学角度看,选择排序的时间复杂度,又是多少呢？
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N But it's definitely not one and in fact it wasn't N in the case of Selection Sort because remember the algorithm we implemented on stage last week had me going back and forth across the stage selecting on iteration, the smallest person I can find, the smallest number and then putting them into place.
但在选择排序中，肯定不会是1，也不是,注意，上周我们在这儿,实现的算法中，反复地,迭代进行选择，选出最小的数,然后将其放在合适的位置。
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Blah, try again. How to do this sort.
首先我想说的是被称作选择排序的算法。
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How many swaps do I do in selection sort?
那选择排序要做多少次交换呢？
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Well, let's go ahead and restore this to, let's say, bubble.
下面选择左边进行冒泡排序。
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Selection Sort.
选择排序。
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I chose Bubble Sort on the left Selection Sort on the right and then something called merge sort on the very right hand side and then I started this all off roughly at the same time and what was frankly striking at least to me at the time was, my God it's done.
我在左边选择冒泡排序，在中间选选择排序,在最右边选择归并排序,然后同时将它们启动,在那时，至少我是震惊了,天哪，它已经完成了。
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Like what the heck have we been spending our time for-- our time on with Bubble Sort and with Selection Sort and in fact there's plenty of other N squared sorts that we're not even gonna bother looking at.
真见鬼，我们竟然在-,冒泡排序和选择排序上花时间,而事实上，还有很多我们根本都不想考虑的,复杂度为N平方的排序方法。
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I was just finding very tunnel vision-like, the smallest elements at that moment in time which means I don't know anything about the other elements other than they are not the smallest and so no matter what with Selection Sort I had to repeat this again and again and again and if you do out the math it's roughly N squared steps in the worst case as well.
我只有一个狭窄的视野，只知道某时刻的最小元素,就意味着我并不知道其他元素的任何情况,只知道它们不是最小的,所以不管怎样，在选择排序中,我就得一遍一遍地重复选择过程,在最坏情况下,大概需要N的平方次比较。
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