计算图中节点介数中心性的函数

function [bc,E] = betweenness_centrality(A,varargin)
% BETWEENNESS_CENTRALITY Compute the betweenness centrality for vertices.
%
% bc = betweenness_centrality(A) returns the betweenness centrality for
% all vertices in A.  
%
% [bc,E] = betweenness_centrality(A) returns the betweenness centrality for
% all vertices in A along with a sparse matrix with the centrality for each
% edge.  
%
% This method works on weighted or weighted directed graphs.
% For unweighted graphs (options.unweighted=1), the runtime is O(VE).
% For weighted graphs, the runtime is O(VE + V(V+E)log(V)).
%
% ... = betweenness_centrality(A,...) takes a set of
% key-value pairs or an options structure.  See set_matlab_bgl_options
% for the standard options. 
%   options.unweighted: use the slightly more efficient unweighted
%     algorithm in the case where all edge-weights are equal [{0} | 1]  
%   options.ec_list: do not form the sparse matrix with edge [{0} | 1]
%   options.edge_weight: a double array over the edges with an edge
%       weight for each node, see EDGE_INDEX and EXAMPLES/REWEIGHTED_GRAPHS
%       for information on how to use this option correctly
%       [{'matrix'} | length(nnz(A)) double vector]
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% Note: the edge centrality can also be returned as an edge list using the
% options.ec_list options.  This option can eliminate some ambiguity in the
% output matrix E when the edge centrality of an edge is 0 and Matlab drops
% the edge from the sparse matrix.  
%