Merge pull request #10 from kiruba-r11/feature-1

Cycle Detection in Undirected Graph using BFS added

C++/Graph Algorithms/undirectedGraphCycleDetectionBFS.cpp

@@ -0,0 +1,96 @@
+#include <iostream>
+#include <vector>
+#include <queue>
+
+using namespace std;
+
+// Graph's node class definition
+class node {
+
+    public:
+        int src;
+        int dest;
+        int wt;
+
+        node(int src , int dest , int wt) {
+            this->src = src;
+            this->dest = dest;
+            this->wt = wt;
+        }
+};
+
+// Function to perform BFS and detect whether the component of the graph has a cycle or not
+bool hasCycleBFS(vector <vector <node> > &graph , vector <bool> &visited , int i) {
+
+    queue <pair <int , int> > q;
+    q.push(make_pair(i , -1));
+    visited[i] = true;
+
+    while(!q.empty()) {
+        int src = q.front().first;
+        int parent = q.front().second;
+
+        q.pop();
+
+        for(int adj = 0; adj < graph[src].size(); adj++) {
+            int dest = graph[src][adj].dest;
+            if(visited[dest] == false) {
+                q.push(make_pair(dest , src));
+                visited[dest] = true;
+            } else {
+                if(dest != parent) return true;
+            }
+        }
+
+    }
+    return false;
+}
+
+int main() {
+
+    int vertices , edges;
+    cin >> vertices >> edges;
+
+    vector <vector <node> > graph(vertices);
+    for(int i = 0; i < edges; i++) {
+
+        int src , dest , wt;
+        cin >> src >> dest >> wt;
+
+        graph[src].push_back(node(src , dest , wt));
+        graph[dest].push_back(node(dest , src , wt));
+    }
+
+    bool hasCycle = false;
+
+    vector <bool> visited(vertices , false);
+    for(int i = 0; i < vertices; i++) {
+        if(!visited[i]) {
+            if(hasCycleBFS(graph , visited , i)) {
+                hasCycle = true;
+                break;
+            }
+        }
+    }
+
+    if(hasCycle) {
+        cout << "There is a Cycle" << endl;
+    } else {
+        cout << "There is No Cycle" << endl;
+    }
+
+    return 0;
+}
+
+// 11
+// 9
+// 0 1 0
+// 1 3 0
+// 2 4 0
+// 4 9 0
+// 4 5 0
+// 5 6 0
+// 7 8 0
+// 8 9 0
+// 7 10 0
+// 6 7 0