Description of contract

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contract

PURPOSE

contract(g,u,v) --- contract v into u

SYNOPSIS

function contract(g,u,v)

DESCRIPTION

 contract(g,u,v) --- contract v into u
 All neighbors of v are added to the neighborhood of u, 
 and then v is deleted. (When v is deleted, vertices that have higher
 index than v are renumbered.)

CROSS-REFERENCE INFORMATION

This function calls:

• add add --- add edge(s) to the graph
• delete delete --- delete vertices or edges from a graph
• neighbors neighbors(g,v) --- neighbors of v as a list.
• nv nv(g) --- number of vertices in g

This function is called by:

SOURCE CODE

0001 function contract(g,u,v)
0002 % contract(g,u,v) --- contract v into u
0003 % All neighbors of v are added to the neighborhood of u,
0004 % and then v is deleted. (When v is deleted, vertices that have higher
0005 % index than v are renumbered.)
0006 
0007 n = nv(g);
0008 
0009 if (u<0) | (u>n) | (v<0) | (v>n) | (u==v) 
0010     return
0011 end
0012 
0013 nlist = neighbors(g,v);
0014 
0015 for x = nlist;
0016     if (x ~= u)
0017         add(g,u,x)
0018     end
0019 end
0020 
0021 delete(g,v);

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