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<a href="#pub-static-methods">Static Public Member Functions</a> &#124;
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<div class="headertitle"><div class="title">CycleCheck Class Reference</div></div>
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Static Public Member Functions</h2></td></tr>
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<tr class="memitem:a399292a33edf87499daa52b51315aca5" id="r_a399292a33edf87499daa52b51315aca5"><td class="memItemLeft" align="right" valign="top">static bool&#160;</td><td class="memItemRight" valign="bottom"><a class="el" href="#a399292a33edf87499daa52b51315aca5">isCyclicBFS</a> (<a class="el" href="../../da/d9a/class_graph.html">Graph</a> const &amp;graph)</td></tr>
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Private Types</h2></td></tr>
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, <b>in_stack</b>
, <b>visited</b>
}</td></tr>
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Static Private Member Functions</h2></td></tr>
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<a name="details" id="details"></a><h2 class="groupheader">Detailed Description</h2>
<div class="textblock"><p>Check if a directed graph has a cycle or not.</p>
<p>This class provides 2 methods to check for cycle in a directed graph: isCyclicDFS &amp; isCyclicBFS.</p>
<ul>
<li>isCyclicDFS uses DFS traversal method to check for cycle in a graph.</li>
<li>isCyclidBFS used BFS traversal method to check for cycle in a graph. </li>
</ul>
<p class="definition">Definition at line <a class="el" href="../../d3/dec/cycle__check__directed__graph_8cpp_source.html#l00159">159</a> of file <a class="el" href="../../d3/dec/cycle__check__directed__graph_8cpp_source.html">cycle_check_directed_graph.cpp</a>.</p>
</div><h2 class="groupheader">Member Enumeration Documentation</h2>
<a id="ae68a1f08ee8c0b6323ab0f281862eadf" name="ae68a1f08ee8c0b6323ab0f281862eadf"></a>
<h2 class="memtitle"><span class="permalink"><a href="#ae68a1f08ee8c0b6323ab0f281862eadf">&#9670;&#160;</a></span>nodeStates</h2>
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<td class="memname">enum CycleCheck::nodeStates : uint8_t</td>
</tr>
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<span class="mlabels"><span class="mlabel private">private</span></span> </td>
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<p class="definition">Definition at line <a class="el" href="../../d3/dec/cycle__check__directed__graph_8cpp_source.html#l00161">161</a> of file <a class="el" href="../../d3/dec/cycle__check__directed__graph_8cpp_source.html">cycle_check_directed_graph.cpp</a>.</p>
<div class="fragment"><div class="line"><span class="lineno"> 161</span>: uint8_t { not_visited = 0, in_stack, visited };</div>
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<h2 class="groupheader">Member Function Documentation</h2>
<a id="a399292a33edf87499daa52b51315aca5" name="a399292a33edf87499daa52b51315aca5"></a>
<h2 class="memtitle"><span class="permalink"><a href="#a399292a33edf87499daa52b51315aca5">&#9670;&#160;</a></span>isCyclicBFS()</h2>
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<td class="memname">static bool CycleCheck::isCyclicBFS </td>
<td>(</td>
<td class="paramtype"><a class="el" href="../../da/d9a/class_graph.html">Graph</a> const &amp;</td> <td class="paramname"><span class="paramname"><em>graph</em></span></td><td>)</td>
<td></td>
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<p>Check if a graph has cycle or not.</p>
<p>This function uses BFS to check if a graph is cyclic or not.</p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">graph</td><td>which needs to be evaluated for the presence of cycle. </td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>true if a cycle is detected, else false. </dd></dl>
<p class="definition">Definition at line <a class="el" href="../../d3/dec/cycle__check__directed__graph_8cpp_source.html#l00250">250</a> of file <a class="el" href="../../d3/dec/cycle__check__directed__graph_8cpp_source.html">cycle_check_directed_graph.cpp</a>.</p>
<div class="fragment"><div class="line"><span class="lineno"> 250</span> {</div>
<div class="line"><span class="lineno"> 251</span> <span class="keyword">auto</span> graphAjdList = graph.getAdjList();</div>
<div class="line"><span class="lineno"> 252</span> <span class="keyword">auto</span> vertices = graph.getVertices();</div>
<div class="line"><span class="lineno"> 253</span> </div>
<div class="line"><span class="lineno"> 254</span> std::vector&lt;unsigned int&gt; indegree(vertices, 0);</div>
<div class="line"><span class="lineno"> 255</span> <span class="comment">// Calculate the indegree i.e. the number of incident edges to the node.</span></div>
<div class="line"><span class="lineno"> 256</span> <span class="keywordflow">for</span> (<span class="keyword">auto</span> <span class="keyword">const</span>&amp; list : graphAjdList) {</div>
<div class="line"><span class="lineno"> 257</span> <span class="keyword">auto</span> children = list.second;</div>
<div class="line"><span class="lineno"> 258</span> <span class="keywordflow">for</span> (<span class="keyword">auto</span> <span class="keyword">const</span>&amp; child : children) {</div>
<div class="line"><span class="lineno"> 259</span> indegree[child]++;</div>
<div class="line"><span class="lineno"> 260</span> }</div>
<div class="line"><span class="lineno"> 261</span> }</div>
<div class="line"><span class="lineno"> 262</span> </div>
<div class="line"><span class="lineno"> 263</span> std::queue&lt;unsigned int&gt; can_be_solved;</div>
<div class="line"><span class="lineno"> 264</span> <span class="keywordflow">for</span> (<span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> <a class="code hl_typedef" href="../../d8/dee/avltree_8cpp.html#a74f0cf18a0e5b832d9994e2f2d022287">node</a> = 0; <a class="code hl_typedef" href="../../d8/dee/avltree_8cpp.html#a74f0cf18a0e5b832d9994e2f2d022287">node</a> &lt; vertices; <a class="code hl_typedef" href="../../d8/dee/avltree_8cpp.html#a74f0cf18a0e5b832d9994e2f2d022287">node</a>++) {</div>
<div class="line"><span class="lineno"> 265</span> <span class="comment">// If a node doesn&#39;t have any input edges, then that node will</span></div>
<div class="line"><span class="lineno"> 266</span> <span class="comment">// definately not result in a cycle and can be visited safely.</span></div>
<div class="line"><span class="lineno"> 267</span> <span class="keywordflow">if</span> (!indegree[<a class="code hl_typedef" href="../../d8/dee/avltree_8cpp.html#a74f0cf18a0e5b832d9994e2f2d022287">node</a>]) {</div>
<div class="line"><span class="lineno"> 268</span> can_be_solved.emplace(<a class="code hl_typedef" href="../../d8/dee/avltree_8cpp.html#a74f0cf18a0e5b832d9994e2f2d022287">node</a>);</div>
<div class="line"><span class="lineno"> 269</span> }</div>
<div class="line"><span class="lineno"> 270</span> }</div>
<div class="line"><span class="lineno"> 271</span> </div>
<div class="line"><span class="lineno"> 272</span> <span class="comment">// Vertices that need to be traversed.</span></div>
<div class="line"><span class="lineno"> 273</span> <span class="keyword">auto</span> remain = vertices;</div>
<div class="line"><span class="lineno"> 274</span> <span class="comment">// While there are safe nodes that we can visit.</span></div>
<div class="line"><span class="lineno"> 275</span> <span class="keywordflow">while</span> (!can_be_solved.empty()) {</div>
<div class="line"><span class="lineno"> 276</span> <span class="keyword">auto</span> solved = can_be_solved.front();</div>
<div class="line"><span class="lineno"> 277</span> <span class="comment">// Visit the node.</span></div>
<div class="line"><span class="lineno"> 278</span> can_be_solved.pop();</div>
<div class="line"><span class="lineno"> 279</span> <span class="comment">// Decrease number of nodes that need to be traversed.</span></div>
<div class="line"><span class="lineno"> 280</span> remain--;</div>
<div class="line"><span class="lineno"> 281</span> </div>
<div class="line"><span class="lineno"> 282</span> <span class="comment">// Visit all the children of the visited node.</span></div>
<div class="line"><span class="lineno"> 283</span> <span class="keyword">auto</span> it = graphAjdList.find(solved);</div>
<div class="line"><span class="lineno"> 284</span> <span class="keywordflow">if</span> (it != graphAjdList.end()) {</div>
<div class="line"><span class="lineno"> 285</span> <span class="keywordflow">for</span> (<span class="keyword">auto</span> child : it-&gt;second) {</div>
<div class="line"><span class="lineno"> 286</span> <span class="comment">// Check if we can visited the node safely.</span></div>
<div class="line"><span class="lineno"> 287</span> <span class="keywordflow">if</span> (--indegree[child] == 0) {</div>
<div class="line"><span class="lineno"> 288</span> <span class="comment">// if node can be visited safely, then add that node to</span></div>
<div class="line"><span class="lineno"> 289</span> <span class="comment">// the visit queue.</span></div>
<div class="line"><span class="lineno"> 290</span> can_be_solved.emplace(child);</div>
<div class="line"><span class="lineno"> 291</span> }</div>
<div class="line"><span class="lineno"> 292</span> }</div>
<div class="line"><span class="lineno"> 293</span> }</div>
<div class="line"><span class="lineno"> 294</span> }</div>
<div class="line"><span class="lineno"> 295</span> </div>
<div class="line"><span class="lineno"> 296</span> <span class="comment">// If there are still nodes that we can&#39;t visit, then it means that</span></div>
<div class="line"><span class="lineno"> 297</span> <span class="comment">// there is a cycle and return true, else return false.</span></div>
<div class="line"><span class="lineno"> 298</span> <span class="keywordflow">return</span> !(remain == 0);</div>
<div class="line"><span class="lineno"> 299</span> }</div>
<div class="ttc" id="aavltree_8cpp_html_a74f0cf18a0e5b832d9994e2f2d022287"><div class="ttname"><a href="../../d8/dee/avltree_8cpp.html#a74f0cf18a0e5b832d9994e2f2d022287">node</a></div><div class="ttdeci">struct node { int data; int height; struct node *left; struct node *right;} node</div><div class="ttdoc">for std::queue</div><div class="ttdef"><b>Definition</b> <a href="../../d8/dee/avltree_8cpp_source.html#l00013">avltree.cpp:13</a></div></div>
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<a id="ad9a270ffba3a68539b92272c702e3474" name="ad9a270ffba3a68539b92272c702e3474"></a>
<h2 class="memtitle"><span class="permalink"><a href="#ad9a270ffba3a68539b92272c702e3474">&#9670;&#160;</a></span>isCyclicDFS()</h2>
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<td class="memname">static bool CycleCheck::isCyclicDFS </td>
<td>(</td>
<td class="paramtype"><a class="el" href="../../da/d9a/class_graph.html">Graph</a> const &amp;</td> <td class="paramname"><span class="paramname"><em>graph</em></span></td><td>)</td>
<td></td>
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<p>Driver function to check if a graph has a cycle.</p>
<p>This function uses DFS to check for cycle in the graph.</p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">graph</td><td>which needs to be evaluated for the presence of cycle. </td></tr>
</table>
</dd>
</dl>
<dl class="section return"><dt>Returns</dt><dd>true if a cycle is detected, else false. </dd></dl>
<p>State of the node.</p>
<p>It is a vector of "nodeStates" which represents the state node is in. It can take only 3 values: "not_visited", "in_stack", and "visited".</p>
<p>Initially, all nodes are in "not_visited" state.</p>
<p class="definition">Definition at line <a class="el" href="../../d3/dec/cycle__check__directed__graph_8cpp_source.html#l00213">213</a> of file <a class="el" href="../../d3/dec/cycle__check__directed__graph_8cpp_source.html">cycle_check_directed_graph.cpp</a>.</p>
<div class="fragment"><div class="line"><span class="lineno"> 213</span> {</div>
<div class="line"><span class="lineno"> 214</span> <span class="keyword">auto</span> vertices = graph.getVertices();</div>
<div class="line"><span class="lineno"> 215</span></div>
<div class="line"><span class="lineno"> 223</span> std::vector&lt;nodeStates&gt; state(vertices, not_visited);</div>
<div class="line"><span class="lineno"> 224</span> </div>
<div class="line"><span class="lineno"> 225</span> <span class="comment">// Start visiting each node.</span></div>
<div class="line"><span class="lineno"> 226</span> <span class="keywordflow">for</span> (<span class="keywordtype">unsigned</span> <span class="keywordtype">int</span> <a class="code hl_typedef" href="../../d8/dee/avltree_8cpp.html#a74f0cf18a0e5b832d9994e2f2d022287">node</a> = 0; <a class="code hl_typedef" href="../../d8/dee/avltree_8cpp.html#a74f0cf18a0e5b832d9994e2f2d022287">node</a> &lt; vertices; <a class="code hl_typedef" href="../../d8/dee/avltree_8cpp.html#a74f0cf18a0e5b832d9994e2f2d022287">node</a>++) {</div>
<div class="line"><span class="lineno"> 227</span> <span class="comment">// If a node is not visited, only then check for presence of cycle.</span></div>
<div class="line"><span class="lineno"> 228</span> <span class="comment">// There is no need to check for presence of cycle for a visited</span></div>
<div class="line"><span class="lineno"> 229</span> <span class="comment">// node as it has already been checked for presence of cycle.</span></div>
<div class="line"><span class="lineno"> 230</span> <span class="keywordflow">if</span> (state[<a class="code hl_typedef" href="../../d8/dee/avltree_8cpp.html#a74f0cf18a0e5b832d9994e2f2d022287">node</a>] == not_visited) {</div>
<div class="line"><span class="lineno"> 231</span> <span class="comment">// Check for cycle.</span></div>
<div class="line"><span class="lineno"> 232</span> <span class="keywordflow">if</span> (<a class="code hl_function" href="#a2f4485c08b45e7a21a2e86f9c3f01d8b">isCyclicDFSHelper</a>(graph.getAdjList(), &amp;state, <a class="code hl_typedef" href="../../d8/dee/avltree_8cpp.html#a74f0cf18a0e5b832d9994e2f2d022287">node</a>)) {</div>
<div class="line"><span class="lineno"> 233</span> <span class="keywordflow">return</span> <span class="keyword">true</span>;</div>
<div class="line"><span class="lineno"> 234</span> }</div>
<div class="line"><span class="lineno"> 235</span> }</div>
<div class="line"><span class="lineno"> 236</span> }</div>
<div class="line"><span class="lineno"> 237</span> </div>
<div class="line"><span class="lineno"> 238</span> <span class="comment">// All nodes have been safely traversed, that means there is no cycle in</span></div>
<div class="line"><span class="lineno"> 239</span> <span class="comment">// the graph. Return false.</span></div>
<div class="line"><span class="lineno"> 240</span> <span class="keywordflow">return</span> <span class="keyword">false</span>;</div>
<div class="line"><span class="lineno"> 241</span> }</div>
<div class="ttc" id="aclass_cycle_check_html_a2f4485c08b45e7a21a2e86f9c3f01d8b"><div class="ttname"><a href="#a2f4485c08b45e7a21a2e86f9c3f01d8b">CycleCheck::isCyclicDFSHelper</a></div><div class="ttdeci">static bool isCyclicDFSHelper(AdjList const &amp;adjList, std::vector&lt; nodeStates &gt; *state, unsigned int node)</div><div class="ttdef"><b>Definition</b> <a href="../../d3/dec/cycle__check__directed__graph_8cpp_source.html#l00171">cycle_check_directed_graph.cpp:171</a></div></div>
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<h2 class="memtitle"><span class="permalink"><a href="#a2f4485c08b45e7a21a2e86f9c3f01d8b">&#9670;&#160;</a></span>isCyclicDFSHelper()</h2>
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<td class="memname">static bool CycleCheck::isCyclicDFSHelper </td>
<td>(</td>
<td class="paramtype">AdjList const &amp;</td> <td class="paramname"><span class="paramname"><em>adjList</em></span>, </td>
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<td class="paramtype">std::vector&lt; nodeStates &gt; *</td> <td class="paramname"><span class="paramname"><em>state</em></span>, </td>
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<td class="paramtype">unsigned int</td> <td class="paramname"><span class="paramname"><em>node</em></span>&#160;)</td>
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<p>Helper function of "isCyclicDFS".</p>
<dl class="params"><dt>Parameters</dt><dd>
<table class="params">
<tr><td class="paramname">adjList</td><td>is the adjacency list representation of some graph. </td></tr>
<tr><td class="paramname">state</td><td>is the state of the nodes of the graph. </td></tr>
<tr><td class="paramname">node</td><td>is the node being evaluated.</td></tr>
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<dl class="section return"><dt>Returns</dt><dd>true if graph has a cycle, else false. </dd></dl>
<p class="definition">Definition at line <a class="el" href="../../d3/dec/cycle__check__directed__graph_8cpp_source.html#l00171">171</a> of file <a class="el" href="../../d3/dec/cycle__check__directed__graph_8cpp_source.html">cycle_check_directed_graph.cpp</a>.</p>
<div class="fragment"><div class="line"><span class="lineno"> 173</span> {</div>
<div class="line"><span class="lineno"> 174</span> <span class="comment">// Add node &quot;in_stack&quot; state.</span></div>
<div class="line"><span class="lineno"> 175</span> (*state)[<a class="code hl_typedef" href="../../d8/dee/avltree_8cpp.html#a74f0cf18a0e5b832d9994e2f2d022287">node</a>] = in_stack;</div>
<div class="line"><span class="lineno"> 176</span> </div>
<div class="line"><span class="lineno"> 177</span> <span class="comment">// If the node has children, then recursively visit all children of the</span></div>
<div class="line"><span class="lineno"> 178</span> <span class="comment">// node.</span></div>
<div class="line"><span class="lineno"> 179</span> <span class="keyword">auto</span> <span class="keyword">const</span> it = adjList.find(<a class="code hl_typedef" href="../../d8/dee/avltree_8cpp.html#a74f0cf18a0e5b832d9994e2f2d022287">node</a>);</div>
<div class="line"><span class="lineno"> 180</span> <span class="keywordflow">if</span> (it != adjList.end()) {</div>
<div class="line"><span class="lineno"> 181</span> <span class="keywordflow">for</span> (<span class="keyword">auto</span> child : it-&gt;second) {</div>
<div class="line"><span class="lineno"> 182</span> <span class="comment">// If state of child node is &quot;not_visited&quot;, evaluate that child</span></div>
<div class="line"><span class="lineno"> 183</span> <span class="comment">// for presence of cycle.</span></div>
<div class="line"><span class="lineno"> 184</span> <span class="keyword">auto</span> state_of_child = (*state)[child];</div>
<div class="line"><span class="lineno"> 185</span> <span class="keywordflow">if</span> (state_of_child == not_visited) {</div>
<div class="line"><span class="lineno"> 186</span> <span class="keywordflow">if</span> (<a class="code hl_function" href="#a2f4485c08b45e7a21a2e86f9c3f01d8b">isCyclicDFSHelper</a>(adjList, state, child)) {</div>
<div class="line"><span class="lineno"> 187</span> <span class="keywordflow">return</span> <span class="keyword">true</span>;</div>
<div class="line"><span class="lineno"> 188</span> }</div>
<div class="line"><span class="lineno"> 189</span> } <span class="keywordflow">else</span> <span class="keywordflow">if</span> (state_of_child == in_stack) {</div>
<div class="line"><span class="lineno"> 190</span> <span class="comment">// If child node was &quot;in_stack&quot;, then that means that there</span></div>
<div class="line"><span class="lineno"> 191</span> <span class="comment">// is a cycle in the graph. Return true for presence of the</span></div>
<div class="line"><span class="lineno"> 192</span> <span class="comment">// cycle.</span></div>
<div class="line"><span class="lineno"> 193</span> <span class="keywordflow">return</span> <span class="keyword">true</span>;</div>
<div class="line"><span class="lineno"> 194</span> }</div>
<div class="line"><span class="lineno"> 195</span> }</div>
<div class="line"><span class="lineno"> 196</span> }</div>
<div class="line"><span class="lineno"> 197</span> </div>
<div class="line"><span class="lineno"> 198</span> <span class="comment">// Current node has been evaluated for the presence of cycle and had no</span></div>
<div class="line"><span class="lineno"> 199</span> <span class="comment">// cycle. Mark current node as &quot;visited&quot;.</span></div>
<div class="line"><span class="lineno"> 200</span> (*state)[<a class="code hl_typedef" href="../../d8/dee/avltree_8cpp.html#a74f0cf18a0e5b832d9994e2f2d022287">node</a>] = visited;</div>
<div class="line"><span class="lineno"> 201</span> <span class="comment">// Return that current node didn&#39;t result in any cycles.</span></div>
<div class="line"><span class="lineno"> 202</span> <span class="keywordflow">return</span> <span class="keyword">false</span>;</div>
<div class="line"><span class="lineno"> 203</span> }</div>
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