an class="lineno">   35</span>&#160;<span class="comment">// and Tarjan (1975). Efficiency of a Good But Not Linear Set</span></div>
<div class="line"><a name="l00036"></a><span class="lineno">   36</span>&#160;<span class="comment">// Union Algorithm. Journal of the ACM 22(2):215-225</span></div>
<div class="line"><a name="l00037"></a><span class="lineno">   37</span>&#160;<span class="comment">// It is implemented as a template so that the size of NodeIndex can be chosen</span></div>
<div class="line"><a 