Merge pull request #116 from ashish1500616/TarjansAlgorithm

#55 Implementation of Tarajan's Algorithm In cpp.

Author: matthewsamuel95

Graph/TarganSCC/TarjansAlgorithm.cpp

@@ -0,0 +1,156 @@
+#include<iostream>
+#include <list>
+#include <stack>
+#define NIL -1
+using namespace std;
+
+class Graph
+{
+    int V;   
+    list<int> *adj;  
+ 
+   
+    void SCCUtil(int u, int disc[], int low[],
+                 stack<int> *st, bool stackMember[]);
+public:
+    Graph(int V);   
+    void addEdge(int v, int w);   
+    void SCC();   
+};
+ 
+Graph::Graph(int V)
+{
+    this->V = V;
+    adj = new list<int>[V];
+}
+ 
+void Graph::addEdge(int v, int w)
+{
+    adj[v].push_back(w);
+}
+ 
+
+void Graph::SCCUtil(int u, int disc[], int low[], stack<int> *st,
+                    bool stackMember[])
+{
+  
+    static int time = 0;
+ 
+    disc[u] = low[u] = ++time;
+    st->push(u);
+    stackMember[u] = true;
+ 
+    
+    list<int>::iterator i;
+    for (i = adj[u].begin(); i != adj[u].end(); ++i)
+    {
+        int v = *i; 
+ 
+  
+        if (disc[v] == -1)
+        {
+            SCCUtil(v, disc, low, st, stackMember);
+ 
+           
+            low[u]  = min(low[u], low[v]);
+        }
+ 
+        
+        else if (stackMember[v] == true)
+            low[u]  = min(low[u], disc[v]);
+    }
+ 
+    
+    int w = 0;  
+    if (low[u] == disc[u])
+    {
+        while (st->top() != u)
+        {
+            w = (int) st->top();
+            cout << w << " ";
+            stackMember[w] = false;
+            st->pop();
+        }
+        w = (int) st->top();
+        cout << w << "n";
+        stackMember[w] = false;
+        st->pop();
+    }
+}
+ void Graph::SCC()
+{
+    int *disc = new int[V];
+    int *low = new int[V];
+    bool *stackMember = new bool[V];
+    stack<int> *st = new stack<int>();
+ 
+  
+    for (int i = 0; i < V; i++)
+    {
+        disc[i] = NIL;
+        low[i] = NIL;
+        stackMember[i] = false;
+    }
+ 
+   
+    for (int i = 0; i < V; i++)
+        if (disc[i] == NIL)
+            SCCUtil(i, disc, low, st, stackMember);
+}
+ 
+int main()
+{
+    cout << "nSCCs in first graph n";
+    Graph g1(5);
+    g1.addEdge(1, 0);
+    g1.addEdge(0, 2);
+    g1.addEdge(2, 1);
+    g1.addEdge(0, 3);
+    g1.addEdge(3, 4);
+    g1.SCC();
+ 
+    cout << "nSCCs in second graph n";
+    Graph g2(4);
+    g2.addEdge(0, 1);
+    g2.addEdge(1, 2);
+    g2.addEdge(2, 3);
+    g2.SCC();
+ 
+    cout << "nSCCs in third graph n";
+    Graph g3(7);
+    g3.addEdge(0, 1);
+    g3.addEdge(1, 2);
+    g3.addEdge(2, 0);
+    g3.addEdge(1, 3);
+    g3.addEdge(1, 4);
+    g3.addEdge(1, 6);
+    g3.addEdge(3, 5);
+    g3.addEdge(4, 5);
+    g3.SCC();
+ 
+    cout << "nSCCs in fourth graph n";
+    Graph g4(11);
+    g4.addEdge(0,1);g4.addEdge(0,3);
+    g4.addEdge(1,2);g4.addEdge(1,4);
+    g4.addEdge(2,0);g4.addEdge(2,6);
+    g4.addEdge(3,2);
+    g4.addEdge(4,5);g4.addEdge(4,6);
+    g4.addEdge(5,6);g4.addEdge(5,7);g4.addEdge(5,8);g4.addEdge(5,9);
+    g4.addEdge(6,4);
+    g4.addEdge(7,9);
+    g4.addEdge(8,9);
+    g4.addEdge(9,8);
+    g4.SCC();
+ 
+    cout << "nSCCs in fifth graph n";
+    Graph g5(5);
+    g5.addEdge(0,1);
+    g5.addEdge(1,2);
+    g5.addEdge(2,3);
+    g5.addEdge(2,4);
+    g5.addEdge(3,0);
+    g5.addEdge(4,2);
+    g5.SCC();
+ 
+    return 0;
+}