>> [CAR DOOR SHUTTING]

>> [汽車車門關閉]

>> [CAR ENGINE STARTING]

>> [汽車發動機起動]

>> [MUSIC PLAYING]

>> [音樂播放]

>> -Moving right along in search of good times and good news.

>> 右沿搜索-Moving 美好的時光和一個好消息。

With good friends you can't lose.

有了良好的朋友，你不能輸。

>> -This could become a habit.

>> - 這可能會成為一種習慣。

>> -Opportunity knocks Let's just reach out and grab it.

>> -Opportunity敲門讓我們 只要伸出手抓住它。

-Yeah!

是啊！

-Together we'll nab it.

-Together我們逮到它。

-We'll hitch hike, bus, or yellow cab it.

-We'll順利調漲， 公交車，或黃色出租車吧。

-Dammit.

-Dammit。

-We're moving right along.

-We're正確的順動。

-Footloose and fancy free.

-Footloose和花式免費。

-Getting there is half the fun.

-Getting有一半的樂趣。

Come share it with me.

跟我來分享。

>> -We're moving right along.

>> -We're正確的順動。

>> -We're going to share the load.

>> -We're要分擔負載。

>> -We don't need a map to get this show on the road.

>> - 我們並不需要一個地圖 獲得本次車展的道路上。

-Hey Fozzy, I want you to turn left if you come to a fork in the road.

- 嘿Fozzy，我希望你能左轉 如果你來到了一個岔路口。

-Yes, sir.

- 是的，先生。

Turn left at the fork in the road.

左轉，在三岔路口。

Turn left.

左轉。

>> -I don't believe that.

>> - 我不相信。

>> -Cruising right along we found the lights on the highway.

>> -Cruising沿著正確的發現 在高速公路上的燈光。

>> -And your way or my way.

>> - 和你的方式或我的方式。

>> -So trust my navigation.

>> - 所以相信我的導航。

>> -Movie stars with flashy cars and life with the top down.

>> - 電影恆星浮華汽車 和壽命與自上而下。

>> -We're storming the big hills.

>> -We're強攻大陵。

>> -Yeah, storm is right.

>> 是啊，暴風雨是正確的。

Should it be snowing?

是否應該下雪？

>> -No, I don't think so.

>> 不，我不這麼認為。

>> -Moving right along.

>> 沿著正確-Moving。

>> -Footloose and fancy free.

>> -Footloose和花式免費。

>> -You're ready for the big time.

>> -You're準備好大的時間。

>> -Is it ready for me?

>> -is它為我準備好？

>> -Moving right along.

>> 沿著正確-Moving。

Moving right along.

運動沿著正確的。

Moving right along.

運動沿著正確的。

Moving right along.

運動沿著正確的。

-I think you better pull over.

- 我想你最好靠邊停車。

-Yes, sir.

- 是的，先生。

>> [END PLAYBACK]

>> [結束播放]

>> [APPLAUSE]

>> [掌聲]

>> DAVID J. MALAN: This is CS50.

>> DAVID J.馬蘭：這是CS50。

And this is the end of Week 0, but the start of a beautiful friendship.

這是第0週的端部，但 一段美好友誼的開始。

We are so excited to be here at Yale University

我們很高興能成為 這裡在耶魯大學

for the very first time with our friend Scaz, and Jason, and Andy.

對於第一次與我們 朋友Scaz，和Jason，和安迪。

All 40 of CS50's TF's and CA's here at Yale.

的CS50的TF的所有40 和CA在這裡在耶魯大學。

And all of you.

而這一切都是你的。

And in fact, it's probably time to--

而事實上，它可能是時間用於：

>> [APPLAUSE]

>> [掌聲]

>> So, even though most of the lectures will indeed be in Cambridge this year,

>> 所以，儘管大部分的演講 的確將在劍橋今年，

the reality is that by design, and very much deliberately in CS50,

現實情況是，由設計， 很刻意的CS50，

I do think we're nearing the point technologically, and pedagogically,

我認為，我們正在接近的地步 技術和教學上，

where it can be a superior educational experience to engage with some

它可以是一個優越的教育 經驗，與一些

of the course's material online.

課程的材料在網上的。

Indeed, the reality-- and if I believe this philosophically-- is that lectures

事實上，reality--如果我相信 這philosophically--是講座

are not a particularly effective means for delivering

是不是一個特別 為提供有效的手段

fairly complex information.

相當複雜的信息。

Certainly over hour plus long spans of time.

當然，在小時 再加上大跨度的時間。

And indeed every few minutes-- I remember myself in college--

事實上每隔幾個minutes-- 我記得自己在college--

you zone out for a moment, you miss some complex topic,

你掃開了一會兒， 你錯過了一些複雜的問題，

and you're gone pretty much for the next 45 minutes.

和你走了差不多 在接下來的45分鐘。

And the reality is that whether you're here in New Haven or Cambridge

而現實情況是，無論是 你在這裡在紐黑文和劍橋

or beyond, the simplicity of having the ability to pause and fast forward,

或超越，具有簡單 暫停的能力和快進，

rewind, hyperlink to related resources, search full text transcripts

快退，超鏈接到相關的 資源搜索全文成績單

and the like is an opportunity that I dare say for our online students

等是一個機會 我敢說我們的在線學生

well beyond New Haven, offers them an opportunity

遠遠超出了紐黑文， 為他們提供了一個機會，

to really grasp the conceptual material that we

要真正掌握 概念性的材料，我們

introduce in lectures all the better.

講座介紹就更好了。

>> But ultimately in CS50, is the students' experience

>> 但最終在CS50，是 學生的經驗

is characterized so, so much more by the course's problem sets,

的特徵是，這麼多 在課程的習題集，

or weekly programming projects, the course's sections led by the teaching

或每週編程項目， 當然各科為首教學

fellows, the nightly office hours led by the course assistants and the teaching

研究員，夜間辦公時間為首的 過程助理和教學

fellows, and indeed such events as CS50 Puzzle

研究員，實際上這樣的 事件CS50謎

Day, CS50's Hack-a-thon, the CS50 Fair, weekly lunches, and so much more.

當天，CS50的黑客馬拉松，在CS50 公平，每週午餐，和這麼多。

And so whether you're here in New Haven, or tuning in from afar,

所以，無論你在這裡新 紐黑文，或調整從遠方來，

today in Cambridge, and we'll see you again soon,

今天在劍橋，和 我們將再次看到您的到來，

the reality is this is one and the same class.

現實的情況是，這是 一個和相同的類。

And we are so excited to be here all together today.

而我們是如此興奮 在這裡一起今天。

And so at the end of the semester, whether here or afar, well

所以在學期結束時， 無論是在這裡還是遠遠望去，以及

hopefully you wear proudly, happily, and perhaps with a bit of relief,

希望你穿自豪，令人高興的是， 或許有一點緩解，

the shirt that bears witness to you having taken CS50.

這見證襯衫 你已經採取CS50。

>> So where did we leave off on Wednesday?

>> 那麼，我們什麼週三離開了嗎？

We took a look at computational thinking.

我們看了看 計算思維。

And that's toward what we distilled computer science unto, at least

而這對我們蒸餾 計算機科學對，至少

for now.

現在。

But we distilled it little further into at least three components elements.

但是，我們蒸餾水它遠一點為 至少三種組分的元素。

>> Inputs, so what is the problem we're trying to solve?

>> 輸入，所以什麼 問題，我們正在努力解決？

Outputs, what is the answer we're hoping to get?

產出，什麼是 回答我們希望能得到？

And the representation there of.

並表示那裡。

And we won't dwell here on after on binary, or even ASCII,

我們不會住在這裡 後二，甚至是ASCII碼，

and the like so much, but rather take for granted

之類的那麼多，但 而想當然地

that we can represent this information, because the far more interesting parts

我們可以代表這個信息， 因為更為有趣的部分

of those problems are not just the inputs and outputs, but the algorithms

這些問題不只是在 輸入和輸出，但這些算法

that go into solving those problems.

該進入解決這些問題。

>> And you might recall from the other day that we

>> 你可能還記得 有一天，我們

took a fairly traditional concept of looking someone up

花了相當傳統 尋找個人上來概念

in a fairly large phone book, or more generally digitally these days,

在一個相當大的電話簿，或 更普遍的數字，這些天，

just a very large data set.

只是一個非常大的數據集。

A really big contacts list, with lots of names alphabetically sorted.

一個非常大的聯繫人列表，用 很多名稱的字母順序排序。

And we realized that while I could approach this problem simply

我們認識到，儘管我 可以簡單地解決這個問題

by using a linear approach-- page by page,

通過使用線性 approach--逐頁，

or even two's at a time-- we realized that the more intuitive algorithm--

甚至兩公司在我們實現了時間 - 該更直觀算法 -

just kind of dividing and conquering the problem again, and again,

只是種分治 再次問題，並再次，

and again-- halving it with each time, gave us this green result.

和again--它與每個減半 時間，給了我們這個綠色的結果。

And it's so much flatter because it suggests

而且它是如此更平坦 因為它表明

that even as this problem gets bigger and bigger,

即使因為這個問題 變得越來越大，

as is the case these days with data sets and reality-- Facebook and Google

既然是這樣，這些天的數據 集和reality-- Facebook和谷歌

search results and the like-- does our algorithm

搜索結果和 like--做我們的算法

perform just as effectively with those bigger bites

執行一樣有效 與那些更大的叮咬

as it did even with the smaller bites.

因為它沒有甚至更小的叮咬。

>> Now it begs the question, what can we actually solve similarly

>> 現在，它引出了一個問題，是什麼 我們可以真正解決類似

with this kind of intuition?

用這種直覺？

This sort of division and conquering?

這種分裂和征服的？

Well, we could do something like this today here.

那麼，我們可以做些什麼 今天這個樣子這裡。

We could take attendance.

我們可以好好聽講。

So maybe like 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11--

因此，也許像1，2，3，4， 5，6，7，8，9，10，11--

not going to be all that efficient.

不會是所有的高效率。

So wait, grade school.

所以等待，小學。

2, 4, 6, 8, 10, 12, 14, 16, 18 and so forth.

2，4，6，8，10，12，14， 16，18等。

But could we do a little better?

但是，我們可以做的更好一點？

>> I'm pretty sure I can't do this by myself.

>> 我敢肯定，我不能 我自己做到這一點。

So if you'll humor us for just a moment, we brought with us

所以，如果你要的幽默我們只是 一個時刻，我們帶來了我們

an algorithm that's just got three steps,

一種算法是 剛拿到三個步驟，

but it does require-- if you don't mind-- all of us stand up,

但它確實如果require-- 不mind--我們所有的人站起來，

if you would.

如果你會的。

So, with all of us now standing, step one of this algorithm is the following.

因此，所有我們現在站，步 該算法中的一個是如下。

Stand up and assign yourself the number 1.

站起來並分配 自己的號碼1。

So at this point in time, literally everyone in this room

因此，在這個時間點， 從字面上每個人都在這個房間

hopefully is thinking to themselves, however awkwardly, the number 1.

希望在想自己， 但是笨拙，數字1。

>> Now step two of this algorithm is going to involve the following.

>> 現在，第二步，該算法是 將涉及以下內容。

Step two, pair off with someone standing,

步驟二，雙關 與人站立，

add your numbers together, and adopt the sum as your new number.

添加數字加在一起，和 採用的總和作為新的號碼。

Quick sanity check.

快速完整性檢查。

What number is everyone thinking of now?

什麼號碼是每個人想的呢？

>> So 2, except maybe for one, awkward, lonesome person.

>> 所以2，也許除了為一體， 尷尬的，寂寞的人。

If we have an odd number of people in the room.

如果我們有一個奇數 人在房間裡。

So one person might still be the number 1, that's fine.

所以，一個人可能仍然 數字1，這很好。

But step three here, one of you should sit down.

但是，一步三到這一步， 你應該坐下。

The other should go back to step two, and repeat, if you would.

另外應該回到步驟 二，如果你會重複。

>> So if still standing, you should be among those going back to step two.

>> 所以，如果仍然屹立不倒，你應該 在那些回到第二步。

Keep going.

繼續前進。

A few people still standing.

有幾個人還站著。

>> So, if still standing, pair up with someone.

>> 所以，如果仍然屹立不倒， 配對與某人。

All right, dwindling down.

好了，越來越少了。

A few people still standing.

有幾個人還站著。

I'll help if need be.

我會幫助，如果需要的話。

Remember the key takeaway here, is how much faster this is than me counting.

記住關鍵外賣這裡，是怎麼 要快得多，這是比我計數。

>> So let's see.

>> 所以，讓我們來看看。

I can help out.

我可以幫忙。

So what number are you still thinking of?

那麼，什麼數量 你還在想什麼？

>> AUDIENCE: I'm at 44.

>> 聽眾：我在44。

>> DAVID J. MALAN: 44, so you go ahead and sit down.

>> DAVID J.馬蘭：44，所以 你先走一步，坐下。

What number are you thinking of?

什麼號碼，你在想什麼？

AUDIENCE: 74.

聽眾：74。

>> DAVID J. MALAN: 74.

>> DAVID J.馬蘭：74。

All right, go ahead and sit down.

好吧，繼續坐下。

Who else is still standing?

還有誰仍然屹立不倒？

86.

86。

And is anyone else still standing?

而且是其他人還站著？

>> What number?

>> 什麼號碼？

I heard 67.

聽說67。

And then in top?

然後在上面？

32.

32。

Anyone else still standing and thinking of a number?

任何人都還站著 和思考的一個數字？

>> Oh, hi.

>> 哦，你好。

Sorry.

抱歉。

Be right back.

就回來。

42.

42。

Anyone else?

還有其他人？

>> AUDIENCE: 47.

>> 聽眾：47。

>> DAVID J. MALAN: 47.

>> DAVID J.馬蘭：47。

Is anyone else still standing who hasn't been counted?

是任何人都還站著 誰沒有被計算在內？

So the final number of people in a room that has 497 seats is-- all of which

所以，人在一個房間裡最後的數 擁有497個座位is--所有這些

are filled-- is 390.

是filled--是390。

So this is great.

因此，這是偉大的。

>> We will soon discuss the notion of a bug in a computer program.

>> 我們下面將要探討的概念 在一個計算機程序中的錯誤。

But we'll come back to that before long.

但是，我們會回來的，不久。

But in theory, what might have happened just now?

但在理論上，可能是什麼 已經發生了剛才？

So even though there were three big steps to this algorithm, each of those

因此，即使有三大 步驟以這種算法中，每個那些

was just kind of one big operation.

只是其中的一種大的操作。

And there was this cyclicity to it in that if you were still standing,

而有這種週期性吧 原因是，如果你還站著，

you kept going from step three to two, step three to two, step three to two.

你不停地從第三步去二， 一步三到二，一步三到二。

>> But what kept happening on each iteration?

>> 但是，保持發生 在每次迭代？

Each cycle of this loop?

這個循環的每個循環？

What was happening elsewhere in the room?

發生了什麼 其他地方的房？

Not only the same thing, but what was happening to half of you?

不僅同樣的事情，但什麼 正在發生的事情的一半，你呢？

Sitting down.

坐了下來。

And so there in lies this insight, much like the phone book example,

所以有謊言這種認識， 很像電話簿例如

in that if half of you are sitting down each time,

中，如果有一半的你 每次坐了下來，

the problem is starting with maybe 400 people,

該問題已經開始 也許有400人，

then to 200 people, than 100 people, then 50 people, and so forth.

然後，200人，100餘人， 然後50人，等等。

>> And so we whittle down in theory to just one person,

>> 因此，我們在惠特爾下來 理論只是一個人，

thinking of the total value of everyone.

想每個人的總價值。

Now reality, some social dynamics, and some arithmetic errors

現在現實中，一些社會動態， 還有一些算術錯誤

might contribute to that ultimate bug.

可能有助於這一最終的bug。

But in theory, while I was still counting away,

但在理論上，而我 還在指望了，

taking several dozen steps, or hundreds of steps

服用幾十 步驟，或幾百步驟

to count yourselves, to count a roomful of 500 or so people

算呀，算 500左右的人一個屋子

should have taken far fewer steps, because you can only divide 500 and 1/2

應該採取更少的步驟， 因為你只能劃分500和1/2

so many times.

這麼多次。

And so just like with the phone book example the other day,

所以，就像用手機 本書實例有一天，

did we have something logarithmic so to speak,

我們什麼有什麼 對數可以這麼說，

whereby if we were all operating in unison,

因此，如果我們都 統一經營，

and ignoring the addition errors, would we

而忽略了 另外的錯誤，我們會

have achieved exactly that kind of running time?

已經完全實現 那樣的運行時間？

>> Now to be fair, kind of cheated, in that I leveraged another resource.

>> 現在，為了公平起見，一種被騙了，在 我利用其他資源。

Whereas it's just one of me, I leveraged hundreds of you.

雖然這只是我的一個， 我利用數百你。

But that might be said to be an example of parallel processing,

但是，這可以說是一種 例如並行處理，

or a state of art very much in vogue where computers these days have

或藝術的狀態非常流行 其中，電腦這幾天有

multiple CPUs, or more technically, more multiple cores,

多個CPU，或者更 在技​​術上，更多個內核，

and can truly do multiple things at once, much like you

可以真正做到多 件事情，就像你

all we're doing there, in parallel.

我們所做的存在，在並行。

But recall that what we also did on Wednesday

但記得，我們 也做週三

was try to capture this intuition and formalize it in code.

在試圖捕捉這種直覺 並規範它的代碼。

Something like pseudo-code.

像偽代碼。

And in fact, and I hope you'll forgive, it's like 80 degrees in here.

而事實上，我希望你會 原諒，這就像在這裡80度。

So I'm going to take this off for just a little bit.

所以，我要藉此 關閉只是一點點。

What I thought we'd do is transition now to an application whereby

我以為我們會做的是轉變 現在的應用程序，從而

we again engage the audience, but write a program in English

我們再次吸引觀眾的， 但用英語寫一個程序

like syntax, with which to solve this problem here.

像語法，與其中 這裡解決這個問題。

[VIDEO PLAYBACK]

[視頻回放]

-It's peanut butter jelly time.

- 它的花生醬果凍時間。

Peanut butter jelly time.

花生醬果凍時間。

Peanut butter jelly time.

花生醬果凍時間。

>> Way ya!

>> 路亞！

Way ya!

路亞！

Way ya!

路亞！

Way ya!

路亞！

Now there you go!

現在，你去那裡！

There you go!

你去那裡！

There you go!

你去那裡！