Understanding an expression which related to full binary trees












1












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I am quite new to discrete mathematics. I was going through graph and found this expression which was for full binary tree, where $B_h$ represents graph i.e. full binary tree of length/ height h
$B_h := ([2]^{≤h}, {{u,ux} such that uepsilon [2]^{<h}, xepsilon [2]})$



I got confused here. what do $[2]^{≤h}$ and $[2]^{<h}$ mean here, i am quite certain that [2] means {1,2}. But that exponent on the set is quite not clear to me. does that mean cartesian product? I would be thankful for any kind of help. thanks!










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  • $begingroup$
    We can make educated guesses, but also you have some typos in your formula, and for a definitely correct answer you probably want to say something about where this expression comes from so that we have context.
    $endgroup$
    – Misha Lavrov
    Jan 28 at 21:58
















1












$begingroup$


I am quite new to discrete mathematics. I was going through graph and found this expression which was for full binary tree, where $B_h$ represents graph i.e. full binary tree of length/ height h
$B_h := ([2]^{≤h}, {{u,ux} such that uepsilon [2]^{<h}, xepsilon [2]})$



I got confused here. what do $[2]^{≤h}$ and $[2]^{<h}$ mean here, i am quite certain that [2] means {1,2}. But that exponent on the set is quite not clear to me. does that mean cartesian product? I would be thankful for any kind of help. thanks!










share|cite|improve this question











$endgroup$












  • $begingroup$
    We can make educated guesses, but also you have some typos in your formula, and for a definitely correct answer you probably want to say something about where this expression comes from so that we have context.
    $endgroup$
    – Misha Lavrov
    Jan 28 at 21:58














1












1








1





$begingroup$


I am quite new to discrete mathematics. I was going through graph and found this expression which was for full binary tree, where $B_h$ represents graph i.e. full binary tree of length/ height h
$B_h := ([2]^{≤h}, {{u,ux} such that uepsilon [2]^{<h}, xepsilon [2]})$



I got confused here. what do $[2]^{≤h}$ and $[2]^{<h}$ mean here, i am quite certain that [2] means {1,2}. But that exponent on the set is quite not clear to me. does that mean cartesian product? I would be thankful for any kind of help. thanks!










share|cite|improve this question











$endgroup$




I am quite new to discrete mathematics. I was going through graph and found this expression which was for full binary tree, where $B_h$ represents graph i.e. full binary tree of length/ height h
$B_h := ([2]^{≤h}, {{u,ux} such that uepsilon [2]^{<h}, xepsilon [2]})$



I got confused here. what do $[2]^{≤h}$ and $[2]^{<h}$ mean here, i am quite certain that [2] means {1,2}. But that exponent on the set is quite not clear to me. does that mean cartesian product? I would be thankful for any kind of help. thanks!







discrete-mathematics elementary-set-theory graph-theory notation






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edited Jan 28 at 22:09







the hitchhiker

















asked Jan 28 at 21:48









the hitchhikerthe hitchhiker

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  • $begingroup$
    We can make educated guesses, but also you have some typos in your formula, and for a definitely correct answer you probably want to say something about where this expression comes from so that we have context.
    $endgroup$
    – Misha Lavrov
    Jan 28 at 21:58


















  • $begingroup$
    We can make educated guesses, but also you have some typos in your formula, and for a definitely correct answer you probably want to say something about where this expression comes from so that we have context.
    $endgroup$
    – Misha Lavrov
    Jan 28 at 21:58
















$begingroup$
We can make educated guesses, but also you have some typos in your formula, and for a definitely correct answer you probably want to say something about where this expression comes from so that we have context.
$endgroup$
– Misha Lavrov
Jan 28 at 21:58




$begingroup$
We can make educated guesses, but also you have some typos in your formula, and for a definitely correct answer you probably want to say something about where this expression comes from so that we have context.
$endgroup$
– Misha Lavrov
Jan 28 at 21:58










1 Answer
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If you will permit, I am more comfortable thinking of $[2]$ as ${0,1}$.



$[2]^h$ is the Cartesian product of $[2]$ with itself $[h]$ times:
$$
[2]^h=[2]times[2]timesdotstimes[2]cong{(b_1,b_2,dots,b_h)mid b_iin [2]text{ for }1le ile h}
$$



In other words, $[2]^h$ consists of binary sequences of length $h$. Then,
$$
[2]^{le h}=[2]^0cup [2]^1cup dotscup [2]^h
$$

is the set of binary sequences of length at most $h$. That is, $2^{le [h]}$ is not a Cartesian product, but a union of Cartesian products. You can probably imagine now what $[2]^{<h}$ is; it consists of binary sequences whose lengths are strictly less than $h$.



The set of edges is of the form ${u,ux}$, where $u$ is a binary sequence of length less than $h$, and $xin {0,1}$. The multiplication here is concatenation. For example, letting $u=(0,1,0)$, and $x=0$, there is an edge between $(0,1,0)$ and $(0,1,0,0)$; we add a $0$ to the end of $u$ to get its neighbor.






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    $begingroup$

    If you will permit, I am more comfortable thinking of $[2]$ as ${0,1}$.



    $[2]^h$ is the Cartesian product of $[2]$ with itself $[h]$ times:
    $$
    [2]^h=[2]times[2]timesdotstimes[2]cong{(b_1,b_2,dots,b_h)mid b_iin [2]text{ for }1le ile h}
    $$



    In other words, $[2]^h$ consists of binary sequences of length $h$. Then,
    $$
    [2]^{le h}=[2]^0cup [2]^1cup dotscup [2]^h
    $$

    is the set of binary sequences of length at most $h$. That is, $2^{le [h]}$ is not a Cartesian product, but a union of Cartesian products. You can probably imagine now what $[2]^{<h}$ is; it consists of binary sequences whose lengths are strictly less than $h$.



    The set of edges is of the form ${u,ux}$, where $u$ is a binary sequence of length less than $h$, and $xin {0,1}$. The multiplication here is concatenation. For example, letting $u=(0,1,0)$, and $x=0$, there is an edge between $(0,1,0)$ and $(0,1,0,0)$; we add a $0$ to the end of $u$ to get its neighbor.






    share|cite|improve this answer











    $endgroup$


















      1












      $begingroup$

      If you will permit, I am more comfortable thinking of $[2]$ as ${0,1}$.



      $[2]^h$ is the Cartesian product of $[2]$ with itself $[h]$ times:
      $$
      [2]^h=[2]times[2]timesdotstimes[2]cong{(b_1,b_2,dots,b_h)mid b_iin [2]text{ for }1le ile h}
      $$



      In other words, $[2]^h$ consists of binary sequences of length $h$. Then,
      $$
      [2]^{le h}=[2]^0cup [2]^1cup dotscup [2]^h
      $$

      is the set of binary sequences of length at most $h$. That is, $2^{le [h]}$ is not a Cartesian product, but a union of Cartesian products. You can probably imagine now what $[2]^{<h}$ is; it consists of binary sequences whose lengths are strictly less than $h$.



      The set of edges is of the form ${u,ux}$, where $u$ is a binary sequence of length less than $h$, and $xin {0,1}$. The multiplication here is concatenation. For example, letting $u=(0,1,0)$, and $x=0$, there is an edge between $(0,1,0)$ and $(0,1,0,0)$; we add a $0$ to the end of $u$ to get its neighbor.






      share|cite|improve this answer











      $endgroup$
















        1












        1








        1





        $begingroup$

        If you will permit, I am more comfortable thinking of $[2]$ as ${0,1}$.



        $[2]^h$ is the Cartesian product of $[2]$ with itself $[h]$ times:
        $$
        [2]^h=[2]times[2]timesdotstimes[2]cong{(b_1,b_2,dots,b_h)mid b_iin [2]text{ for }1le ile h}
        $$



        In other words, $[2]^h$ consists of binary sequences of length $h$. Then,
        $$
        [2]^{le h}=[2]^0cup [2]^1cup dotscup [2]^h
        $$

        is the set of binary sequences of length at most $h$. That is, $2^{le [h]}$ is not a Cartesian product, but a union of Cartesian products. You can probably imagine now what $[2]^{<h}$ is; it consists of binary sequences whose lengths are strictly less than $h$.



        The set of edges is of the form ${u,ux}$, where $u$ is a binary sequence of length less than $h$, and $xin {0,1}$. The multiplication here is concatenation. For example, letting $u=(0,1,0)$, and $x=0$, there is an edge between $(0,1,0)$ and $(0,1,0,0)$; we add a $0$ to the end of $u$ to get its neighbor.






        share|cite|improve this answer











        $endgroup$



        If you will permit, I am more comfortable thinking of $[2]$ as ${0,1}$.



        $[2]^h$ is the Cartesian product of $[2]$ with itself $[h]$ times:
        $$
        [2]^h=[2]times[2]timesdotstimes[2]cong{(b_1,b_2,dots,b_h)mid b_iin [2]text{ for }1le ile h}
        $$



        In other words, $[2]^h$ consists of binary sequences of length $h$. Then,
        $$
        [2]^{le h}=[2]^0cup [2]^1cup dotscup [2]^h
        $$

        is the set of binary sequences of length at most $h$. That is, $2^{le [h]}$ is not a Cartesian product, but a union of Cartesian products. You can probably imagine now what $[2]^{<h}$ is; it consists of binary sequences whose lengths are strictly less than $h$.



        The set of edges is of the form ${u,ux}$, where $u$ is a binary sequence of length less than $h$, and $xin {0,1}$. The multiplication here is concatenation. For example, letting $u=(0,1,0)$, and $x=0$, there is an edge between $(0,1,0)$ and $(0,1,0,0)$; we add a $0$ to the end of $u$ to get its neighbor.







        share|cite|improve this answer














        share|cite|improve this answer



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        edited Jan 29 at 4:30

























        answered Jan 29 at 3:14









        Mike EarnestMike Earnest

        26.2k22151




        26.2k22151






























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