LichengZhang

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0 years, 93 days

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These are questions asked by LichengZhang

Hi:
 I use the following codes:
with(GraphTheory):
Graphs_data3:=[NonIsomorphicGraphs(6,restrictto =[connected], output
= graphs, outputform =graph)]:
Diameter2_select:=select[flatten](t->Diameter(t)=2,Graphs_data3):
map(DrawGraph,Diameter2_select);
nops(Diameter2_select);

Since  59 graphs are not many, so,I want to display  it. But the list show that
[Length of output exceeds limit of 1000000]`
How do I do?

If I use DrawGraph(Diameter2_select), the output is to large, and it is  not convenient to print it out .

 

 We know the following facts: 

The SequenceGraph command returns a graph with the specified degree sequence given as input, if such a graph exists. It raises an exception otherwise. 
 But  If I  want to get more graphs  that satisfy this condition of degree sequence ? (If graphs are not many ,I want get all graphs better)
what should I do.?
For example: DrawGraph(SequenceGraph([3, 2, 2, 1, 1, 1]));  It returns the first graph below, but it is obvious that the second graph also fits the condition.

squenceGraph.mw

  I want list all  diameter-2  Nonisomorphismgraphs  of order n . I use the following code, but its running speed  is slow with  order of graph gradually increasing . (for example,n=10)
 Are there other ways to Improve it? 
restart:
with(GraphTheory):
Graphs_data:=[NonIsomorphicGraphs(4,restrictto =[connected], output = graphs, outputform =graph)]:
Diameter_select:=select[flatten](t->Diameter(t)=2,Graphs_data):
DrawGraph(Diameter_select,size=[50,50]);

  By the way,  Why doesn't size=[50,50] work ?

 
                       
                   
               
               
           
           
               
                   
                 

  Hello: 
     We know The FindMaximalElement(L) function returns the largest element of the list L .
   My questions is  How do I find the second largest element in a list and its index?  
     Since there are so many lists to consider , Algorithmic Complexity may be as low as possible.
     More generally, we want to find the third-largest  element and so on.
     For instance, Given a list [3,2,3,6,8], we want to get 6 and 4 , since 6 is the  second largest element and 4 is its index. 
    Thank you in advance for your help.
  Licheng

  Hello: 
    As a first step to my question, let  G be  a graph and  I'd like to know  whether it contains a C4 (cycle of 4) as its subgraph.
     For example: .   it contains C4.  So  program may be return true.  
    I'm most concerned about the following thing ( it is important problem for me, since in graphtheory, we usually consider some class graphs contain no sepecific graph ) :
   1 Further , I want to  get all connected graphs of order less than 6  which  contains no C4 .
   2 More generally, I want  to konw  a graph  whether contains some graph as its subgraph.For example : does it contain K4CompleteGraph(4)K32  CompleteGraph(3, 2)  and so on ?
    I read the  function subgaph.  But  It didn't solve my problem. Many thanks for your help or advise.
   # I  just know there is a function  IsTriangleFree which test if graph is triangle-free ( graph comtains no C3 in Maple 2019. I think my question and how to program may be  meaningful.

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