6. Randomization: Matrix Multiply, Quicksort

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  • Опубліковано 25 лис 2024

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  • @karthikvasishtaramesh6382
    @karthikvasishtaramesh6382 8 років тому +112

    Quick Sort: 50:24

    • @ashfaqrahman2795
      @ashfaqrahman2795 7 років тому +2

      Karthik Vasishta Ramesh Hamere bhagwan Amarendra Baahubali ka raqt ho tum

    • @heddygong7416
      @heddygong7416 4 роки тому +3

      Randomized Quick Sort: 1:07:44

    • @sumitlahiri4973
      @sumitlahiri4973 3 роки тому +2

      This is most useful post in the whole "comment section".

    • @brendawilliams8062
      @brendawilliams8062 3 роки тому +1

      @@sumitlahiri4973 no. Just to have the chance. I didn’t like the way they add before and still don’t. I Quit. So go ahead. 😂 lol

    • @tharunreddy7333
      @tharunreddy7333 2 роки тому

      Thanks!

  • @huecountstudio8796
    @huecountstudio8796 8 років тому +36

    MIT has some quality professors, damn. This was very helpful, thank you

  • @seancolandrea1256
    @seancolandrea1256 5 років тому +35

    coming to this from 6.006 feels like martin scorsese directed this

  • @o.y.930
    @o.y.930 3 роки тому +32

    1:19:43 when my professor sees me entering the classrom

  • @cybernagle
    @cybernagle 11 місяців тому

    randomize quick sort & analysis: 1:07:57

  • @adityasanthosh702
    @adityasanthosh702 4 роки тому +12

    "So If You're going to do the same thing again and again,and expect different results, That's called Insanity"

  • @shah.kairav
    @shah.kairav 4 роки тому +4

    Wasn't the professor correct in making the jth value 1 instead of the ith value as pointed out by one of the students?

    • @PierrePark
      @PierrePark 3 роки тому

      the professor was incorrect?

    • @hj2931
      @hj2931 2 роки тому

      I also agree that the professor is correct. For example, if D is a 3 x 2 matrix and v is a 2 x 1 vector, let i = 3, but there is no third row in v.

  • @mohsennabian9661
    @mohsennabian9661 8 років тому +3

    Love double camera!

  • @oronshifman
    @oronshifman Рік тому

    50:00 - quick sort

  • @jayeshmarathe7678
    @jayeshmarathe7678 3 роки тому

    1:07:40 Randomised quicksort

  • @imaddinamsif
    @imaddinamsif 6 років тому +10

    i don't know why i am from spain :( I looked exams from MIT, which were published on official web page and i like it.... Professor? I like how they are proposing some problems and how they teach, This life is not fair, but I will do everything possible to finish and do a master at MIT

    • @artificialintelligence3727
      @artificialintelligence3727 6 років тому +2

      Sorry to break it but MIT gets only PhD as graduate students in CS. Go for a PhD, do research.

    • @imaddinamsif
      @imaddinamsif 4 роки тому

      Brandon Busby i was studing in UPV (Valencia)

  • @ninjacod2254
    @ninjacod2254 6 років тому +4

    Hi Guys,
    How different is this course comparing to the Introduction to Algorithms class taught by him?

    • @F1mus
      @F1mus 4 роки тому +5

      From experience, 6.046 is MUCH harder than 6.006.

    • @dharmiknaik1772
      @dharmiknaik1772 2 роки тому

      6.006 entails analysing algorithms. This class is concerned with more designing an algo.

  • @evanpiermont7490
    @evanpiermont7490 3 роки тому +1

    What is the collection of r vectors? Doesn't the 1-1 mapping argument require that your set of vectors (the support of the randomization) is close under addition by v. But without knowing v ahead of time, this might require an infinite set of vectors, in which case a bijection is not enough to guarantee equal measure between sets.

    • @fbrunodr
      @fbrunodr 2 роки тому

      • r is simply a R^n vector.
      • If D is not 0, then there exists a vector v such that Dv /= 0. You don't need to know v, you just need to know there is v.
      • He is not proving the sets have equal measure. He's proving one set is at least as big as the other.

    • @benihananah
      @benihananah 2 роки тому

      all vectors of size n and entries 0 or 1. it's closed under (+ mod2)

  • @andrasviczian9262
    @andrasviczian9262 4 роки тому +3

    Couldn't you just make r a vector of n ones? Then if D is actually all zeros it would give the right answer, and if D has a one at any place it will also give the right answer.

    • @luojihencha
      @luojihencha 4 роки тому

      I am wondering as well

    • @benihananah
      @benihananah 2 роки тому

      Take A=[[1, 0], [0, 1]], B = [[1, 1], [0, 0]] and C = [[1, 1], [1, 1]]
      AB not= C, but Frievald's alg returns YES for r=[1, 1].
      The proof shows, however, that there exists an r'=[1, 0] such that Frievald's alg returns NO.

  • @gallerycollection2022
    @gallerycollection2022 3 місяці тому

    amaizing

  • @barsopiavivek
    @barsopiavivek 8 років тому +3

    a lot of freebies this lecture

  • @ayushkapri1857
    @ayushkapri1857 5 років тому +3

    Do these lectures only have theory.

  • @mahendraaanjna2005
    @mahendraaanjna2005 3 роки тому

    What does the T mean?

    • @dharmiknaik1772
      @dharmiknaik1772 2 роки тому +1

      They are making fun of the MBTA (public transit system over by MIT).

  • @kartikkankurte717
    @kartikkankurte717 2 місяці тому

    looks like some documentary

  • @veraBeStnews
    @veraBeStnews 4 роки тому

    Does someone know which book he mentions? CLRS

    • @BrandonCGreer
      @BrandonCGreer 4 роки тому

      CLRS is sort of the classic Algorithm book, the letters are the last names of the authors. If you search CLRS pdf, you'll find a link on Github. The third edition is the most recent one, it's more mathematically formal than these lectures.

    • @shershahdrimighdelih
      @shershahdrimighdelih 4 роки тому +1

      Introduction to Algorithms by Cormen, Leiserson, Rivest, Stein. It's in the readings section of the OCW page corresponding to this course. It's a very good book if you're looking to actually understanding how the algorithms work. But it requires a little background on math. 6.006 covers a third of it, and 6.046 covers another third.

  • @इंसान-न4ढ
    @इंसान-न4ढ 5 років тому +11

    LOL at 1:19:44

  • @junweima
    @junweima 6 років тому

    amazing!

  • @VarunRamanathan28031999
    @VarunRamanathan28031999 6 років тому +4

    Watch this in 2x speed.

  • @ChaojianZhang
    @ChaojianZhang 3 роки тому

    This 1080p lecture recording is awesome.

    • @ChaojianZhang
      @ChaojianZhang 3 роки тому

      I finally realize those are more like conference presentations.

    • @ChaojianZhang
      @ChaojianZhang 3 роки тому

      (Note) If no one asks questions for 90% of the time, we should just make those lectures online-access 90% of the time, and let instructors just do Q&A the rest of the time.

    • @ChaojianZhang
      @ChaojianZhang 3 роки тому

      If, however, we can collect all questions specific to a lecture - even that part can be archived.

  • @shohmansur4603
    @shohmansur4603 3 роки тому +1

    Who going to study in MIT ?

  • @jimmypi7
    @jimmypi7 5 років тому

    anyone understand their joke about : probably correct and probably fast algorithm?
    111
    00:06:56,144 --> 00:06:57,560
    which means that
    they're incorrect
    112
    00:06:57,560 --> 00:06:59,560
    and slow some of the time.
    113
    00:06:59,560 --> 00:07:00,100
    Right?
    114
    00:07:00,100 --> 00:07:03,900
    So what do you think those
    algorithms are called?
    115
    00:07:03,900 --> 00:07:04,400
    Sorry.
    116
    00:07:04,400 --> 00:07:05,222
    What?
    117
    00:07:05,222 --> 00:07:06,580
    AUDIENCE: T?
    118
    00:07:06,580 --> 00:07:07,610
    SRINIVAS DEVADAS: The T?
    119
    00:07:07,610 --> 00:07:08,130
    Oh.
    120
    00:07:08,130 --> 00:07:08,330
    Oh!
    121
    00:07:08,330 --> 00:07:09,500
    That deserves a Frisbee.
    122
    00:07:09,500 --> 00:07:10,700
    Oh my goodness!
    123
    00:07:10,700 --> 00:07:11,980
    [LAUGHS] All right.

    • @jimmypi7
      @jimmypi7 5 років тому

      Prof Srini later mentioned :
      133
      00:07:37,479 --> 00:07:38,020
      So the MB/TA.
      And I googled MB/TA :
      ua-cam.com/video/pJDbEuCr7VA/v-deo.html
      BOSTON, riding the SUBWAY (THE 'T') from Boston University to Quincy Market (USA)
      The T is probably boston subway?
      ps , the following is my google attempts : in reverse chronological order
      &q=the+t+in+boston&
      &q=MB%2FTA+the+t+in+boston&
      &q=MB%2FTA&

    • @ChrisSketch89
      @ChrisSketch89 4 роки тому +2

      They’re making fun of MBTA, the public transit system over by MIT.

  • @maashaz
    @maashaz 3 роки тому +1

    feels bad that my professor just copy pastes from MIT
    i dont know why i pay for school...

  • @shahsadponnad6619
    @shahsadponnad6619 4 роки тому +3

    i didnt understand why every one laughed when the student said '"t" .did I miss anything

    • @orifmilod3469
      @orifmilod3469 4 роки тому +6

      The t stands for transportation in Massachusetts, MBTA (Massachusetts Bay Transportation Authority)

    • @shahsadponnad6619
      @shahsadponnad6619 4 роки тому +2

      @@orifmilod3469 thank you. I thought it was some kind of algorithm. 😂

  • @TheEmeraldSwordAxe
    @TheEmeraldSwordAxe 6 років тому +3

    These instructors teach the same class again and again, why cant they write without looking at their notes. It seems that if you take away their notes they will be helpless.

    • @abdu1998a
      @abdu1998a 6 років тому +21

      wtf is wrong with checking notes? They don't need to memorize to teach it. They should just understand it that's all. Also, they can probably remember that without looking at the notes but it may take time. Would it be better if they didn't look at the notes but think 10-15 mins everytime they didn't remember a detail?

    • @pratikkulkarni891
      @pratikkulkarni891 6 років тому +34

      One of the main reasons might be that they don't miss out on any topic and be consistent with the notes that they provide to the students.