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POWhy use DFS to find cycles in an undirected graph and topological sorting to find cycles in a directed graph?
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2013-05-27T19:51:06.330
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For undirected graphs , if we need to find a cycle , we use depth-first search as described <a href="https://stackoverflow.com/questions/526331/cycles-in-an-undirected-graph">in this older question</a>,which is a well known method and also optimal . But for directed graph, <a href="https://stackoverflow.com/questions/583876/how-do-i-check-if-a-directed-graph-is-acyclic">this other question</a> suggests using topological sorting. My question is, why can't we use the same technique we use for undirected graphs, to check for cycles in directed graph? I've thought of various cases and the algorithms always seem to agree. Can anyone come up with some example directed graph where DFS fails to find a cycle but topological sorting does?
Tags
<algorithm><graph><depth-first-search><topological-sort>
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Why use DFS to find cycles in an undirected graph and topological sorting to find cycles in a directed graph?
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1. COby the way topological sort is achieved by doing DFS (there may be other ways too). So consider both of them as same at least in this context.
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