title: Cycles in an Undirected Graph
body: <p>Given an undirected graph <em>G</em>=(<em>V</em>, <em>E</em>) with <em>n</em> vertices (|<em>V</em>| = <em>n</em>), how do you find if it contains a cycle in <em>O</em>(<em>n</em>)?</p>