I am creating a long table in latex and the problem is that there is too much space between the last column and the one before it. Here is my code and the picture of the table:

begin{center}
begin{longtable}[c]{c cc}
caption{Graph embedding techniques: types, used models and algorithms cite{cai2018comprehensive}.label{long}}
\
hline
Graph Embedding Technique & Model Type & Algorithm\ [0.5ex] 
hline  
multirow{11}{*}{Matrix factorization} & multirow{6}{*}{Graph Laplacian Eigenmaps} & Isomap\
~&~& ARE cite{lin2005semantic}\
~&~& LPP cite{he2003locality}\
~&~& SLE cite{gong2014signed}\
~&~& HSL cite{sun2008hypergraph}\
~&~& Diffusion maps\cmidrule{2-3}
&~multirow{7}{*}{Node proximity matrix factorization}&LLE cite{roweis2000nonlinear}\
&~&~CMF cite{}\
&~&~GraRep cite{cao2015grarep}\
&~&~ULGE cite{nie2017unsupervised}\
&~&~FONPE cite{pang2017flexible}\
&~&~SPE cite{shaw2009structure}\
.
.
end{longtable}
end{center}

enter image description here