SecondThread's blog

By SecondThread, history, 11 months ago, In English

Algorithms Dead Episode 1: Division Under Mod

Do you blindly do operations under mod without knowing why they work? Does it scare you when a problem asks you do print something mod a big number? If so, you should watch Episode 1 of Algorithms Dead!

In it, I talk about why mod operations (addition/subtraction/multiplication) are allowed, why mod inverses work, and what things are safe to do when you store fractions as $$$p*q^{-1}$$$.

 
 
 
 
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11 months ago, # |
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It was nice, your channel has many helpful videos,also loved the lecture on Game Theory.

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6 months ago, # |
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@SecondThread : Can you please add some good questions for practice on this topic ?

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3 months ago, # |
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the answer for 8/7(mod 5) = 4 using prime modulo inverse , shouldn't it be 1 ?

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    2 weeks ago, # ^ |
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    The denominator is 7 here, which is congruent to 2(mod 5).

    The multiplicative inverse of 2 under mod 5 is 3.

    So, the expression becomes

    = (8*3)(mod 5)
    = 24(mod 5)
    = 4