Total number of paths between any two nodes - Graph vs. Complete Binary Tree












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$begingroup$


In a graph, the total number of paths between any two nodes, is given by $n!$. Proof is in this link



In a Complete Binary tree, the total number of paths from root to leaf is basically, the number of leaves, which is $2^{log_2n - 1}$ and the time complexity of finding these is $O(n)$ since you would have to visit every node for doing so.



My question is, what is the time complexity of finding all paths between any two nodes in a complete binary tree ? Is it $2^n$ since from any node, you have two paths?



Cross posting from MathOverflow, as this is a more appropriate forum for the discussion in question.










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  • 1




    $begingroup$
    I'm confused... in a tree, there is only ONE path between any two specified nodes.
    $endgroup$
    – Nick Peterson
    Dec 3 '16 at 19:20






  • 1




    $begingroup$
    And also, the claim about graphs is incorrect as stated. The number of paths between two nodes in a graph depends entirely on the structure of the graph -- it may be 0, it may be large. The largest it could ever be, however, is $(n-2)!$, in the complete graph.
    $endgroup$
    – Nick Peterson
    Dec 3 '16 at 19:22










  • $begingroup$
    @NickPeterson, your comment about the number of paths between two gives nodes, being (n-2)! is correct. I meant to say, the number of paths from any node to any other node is n!. Is that correct? About the tree, again, I mean the same thing. What is the total number of paths from root to any/(all) leaves? PS : Editing the question to remove ambiguity.
    $endgroup$
    – learningboy
    Dec 3 '16 at 19:29
















0












$begingroup$


In a graph, the total number of paths between any two nodes, is given by $n!$. Proof is in this link



In a Complete Binary tree, the total number of paths from root to leaf is basically, the number of leaves, which is $2^{log_2n - 1}$ and the time complexity of finding these is $O(n)$ since you would have to visit every node for doing so.



My question is, what is the time complexity of finding all paths between any two nodes in a complete binary tree ? Is it $2^n$ since from any node, you have two paths?



Cross posting from MathOverflow, as this is a more appropriate forum for the discussion in question.










share|cite|improve this question











$endgroup$








  • 1




    $begingroup$
    I'm confused... in a tree, there is only ONE path between any two specified nodes.
    $endgroup$
    – Nick Peterson
    Dec 3 '16 at 19:20






  • 1




    $begingroup$
    And also, the claim about graphs is incorrect as stated. The number of paths between two nodes in a graph depends entirely on the structure of the graph -- it may be 0, it may be large. The largest it could ever be, however, is $(n-2)!$, in the complete graph.
    $endgroup$
    – Nick Peterson
    Dec 3 '16 at 19:22










  • $begingroup$
    @NickPeterson, your comment about the number of paths between two gives nodes, being (n-2)! is correct. I meant to say, the number of paths from any node to any other node is n!. Is that correct? About the tree, again, I mean the same thing. What is the total number of paths from root to any/(all) leaves? PS : Editing the question to remove ambiguity.
    $endgroup$
    – learningboy
    Dec 3 '16 at 19:29














0












0








0





$begingroup$


In a graph, the total number of paths between any two nodes, is given by $n!$. Proof is in this link



In a Complete Binary tree, the total number of paths from root to leaf is basically, the number of leaves, which is $2^{log_2n - 1}$ and the time complexity of finding these is $O(n)$ since you would have to visit every node for doing so.



My question is, what is the time complexity of finding all paths between any two nodes in a complete binary tree ? Is it $2^n$ since from any node, you have two paths?



Cross posting from MathOverflow, as this is a more appropriate forum for the discussion in question.










share|cite|improve this question











$endgroup$




In a graph, the total number of paths between any two nodes, is given by $n!$. Proof is in this link



In a Complete Binary tree, the total number of paths from root to leaf is basically, the number of leaves, which is $2^{log_2n - 1}$ and the time complexity of finding these is $O(n)$ since you would have to visit every node for doing so.



My question is, what is the time complexity of finding all paths between any two nodes in a complete binary tree ? Is it $2^n$ since from any node, you have two paths?



Cross posting from MathOverflow, as this is a more appropriate forum for the discussion in question.







graph-theory algorithms factorial computational-complexity trees






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edited Jan 26 '18 at 0:29









bof

51.5k558120




51.5k558120










asked Dec 3 '16 at 19:08









learningboylearningboy

285




285








  • 1




    $begingroup$
    I'm confused... in a tree, there is only ONE path between any two specified nodes.
    $endgroup$
    – Nick Peterson
    Dec 3 '16 at 19:20






  • 1




    $begingroup$
    And also, the claim about graphs is incorrect as stated. The number of paths between two nodes in a graph depends entirely on the structure of the graph -- it may be 0, it may be large. The largest it could ever be, however, is $(n-2)!$, in the complete graph.
    $endgroup$
    – Nick Peterson
    Dec 3 '16 at 19:22










  • $begingroup$
    @NickPeterson, your comment about the number of paths between two gives nodes, being (n-2)! is correct. I meant to say, the number of paths from any node to any other node is n!. Is that correct? About the tree, again, I mean the same thing. What is the total number of paths from root to any/(all) leaves? PS : Editing the question to remove ambiguity.
    $endgroup$
    – learningboy
    Dec 3 '16 at 19:29














  • 1




    $begingroup$
    I'm confused... in a tree, there is only ONE path between any two specified nodes.
    $endgroup$
    – Nick Peterson
    Dec 3 '16 at 19:20






  • 1




    $begingroup$
    And also, the claim about graphs is incorrect as stated. The number of paths between two nodes in a graph depends entirely on the structure of the graph -- it may be 0, it may be large. The largest it could ever be, however, is $(n-2)!$, in the complete graph.
    $endgroup$
    – Nick Peterson
    Dec 3 '16 at 19:22










  • $begingroup$
    @NickPeterson, your comment about the number of paths between two gives nodes, being (n-2)! is correct. I meant to say, the number of paths from any node to any other node is n!. Is that correct? About the tree, again, I mean the same thing. What is the total number of paths from root to any/(all) leaves? PS : Editing the question to remove ambiguity.
    $endgroup$
    – learningboy
    Dec 3 '16 at 19:29








1




1




$begingroup$
I'm confused... in a tree, there is only ONE path between any two specified nodes.
$endgroup$
– Nick Peterson
Dec 3 '16 at 19:20




$begingroup$
I'm confused... in a tree, there is only ONE path between any two specified nodes.
$endgroup$
– Nick Peterson
Dec 3 '16 at 19:20




1




1




$begingroup$
And also, the claim about graphs is incorrect as stated. The number of paths between two nodes in a graph depends entirely on the structure of the graph -- it may be 0, it may be large. The largest it could ever be, however, is $(n-2)!$, in the complete graph.
$endgroup$
– Nick Peterson
Dec 3 '16 at 19:22




$begingroup$
And also, the claim about graphs is incorrect as stated. The number of paths between two nodes in a graph depends entirely on the structure of the graph -- it may be 0, it may be large. The largest it could ever be, however, is $(n-2)!$, in the complete graph.
$endgroup$
– Nick Peterson
Dec 3 '16 at 19:22












$begingroup$
@NickPeterson, your comment about the number of paths between two gives nodes, being (n-2)! is correct. I meant to say, the number of paths from any node to any other node is n!. Is that correct? About the tree, again, I mean the same thing. What is the total number of paths from root to any/(all) leaves? PS : Editing the question to remove ambiguity.
$endgroup$
– learningboy
Dec 3 '16 at 19:29




$begingroup$
@NickPeterson, your comment about the number of paths between two gives nodes, being (n-2)! is correct. I meant to say, the number of paths from any node to any other node is n!. Is that correct? About the tree, again, I mean the same thing. What is the total number of paths from root to any/(all) leaves? PS : Editing the question to remove ambiguity.
$endgroup$
– learningboy
Dec 3 '16 at 19:29










1 Answer
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$begingroup$

From Wikipeida:




In mathematics, and more specifically in graph theory, a tree is an undirected graph in which any two vertices are connected by exactly one path. In other words, any acyclic connected graph is a tree. A forest is a disjoint union of trees.




I have no idea why you would want all paths between all nodes, but it would probably be bounded by at least $O(n^3)$, since you have $n(n-1)approx O(n^2)$ different nodes to choose from, and most depth-first search algorithms run in $O(n)$ time.



In short: $O(n)$ for finding the singular path between two nodes and $O(n^3)$ for finding all paths between any two nodes.






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    $begingroup$

    From Wikipeida:




    In mathematics, and more specifically in graph theory, a tree is an undirected graph in which any two vertices are connected by exactly one path. In other words, any acyclic connected graph is a tree. A forest is a disjoint union of trees.




    I have no idea why you would want all paths between all nodes, but it would probably be bounded by at least $O(n^3)$, since you have $n(n-1)approx O(n^2)$ different nodes to choose from, and most depth-first search algorithms run in $O(n)$ time.



    In short: $O(n)$ for finding the singular path between two nodes and $O(n^3)$ for finding all paths between any two nodes.






    share|cite|improve this answer









    $endgroup$


















      0












      $begingroup$

      From Wikipeida:




      In mathematics, and more specifically in graph theory, a tree is an undirected graph in which any two vertices are connected by exactly one path. In other words, any acyclic connected graph is a tree. A forest is a disjoint union of trees.




      I have no idea why you would want all paths between all nodes, but it would probably be bounded by at least $O(n^3)$, since you have $n(n-1)approx O(n^2)$ different nodes to choose from, and most depth-first search algorithms run in $O(n)$ time.



      In short: $O(n)$ for finding the singular path between two nodes and $O(n^3)$ for finding all paths between any two nodes.






      share|cite|improve this answer









      $endgroup$
















        0












        0








        0





        $begingroup$

        From Wikipeida:




        In mathematics, and more specifically in graph theory, a tree is an undirected graph in which any two vertices are connected by exactly one path. In other words, any acyclic connected graph is a tree. A forest is a disjoint union of trees.




        I have no idea why you would want all paths between all nodes, but it would probably be bounded by at least $O(n^3)$, since you have $n(n-1)approx O(n^2)$ different nodes to choose from, and most depth-first search algorithms run in $O(n)$ time.



        In short: $O(n)$ for finding the singular path between two nodes and $O(n^3)$ for finding all paths between any two nodes.






        share|cite|improve this answer









        $endgroup$



        From Wikipeida:




        In mathematics, and more specifically in graph theory, a tree is an undirected graph in which any two vertices are connected by exactly one path. In other words, any acyclic connected graph is a tree. A forest is a disjoint union of trees.




        I have no idea why you would want all paths between all nodes, but it would probably be bounded by at least $O(n^3)$, since you have $n(n-1)approx O(n^2)$ different nodes to choose from, and most depth-first search algorithms run in $O(n)$ time.



        In short: $O(n)$ for finding the singular path between two nodes and $O(n^3)$ for finding all paths between any two nodes.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Dec 3 '16 at 19:31









        AlgorithmsXAlgorithmsX

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