Merge pull request #17 from PrajwalAdsul/master

added strongly connected components for graph

Author: GouravSingh2580

Graphs1/strongly_connected_components.cpp

@@ -0,0 +1,90 @@
+// Strongly connected components of graph
+#include<bits/stdc++.h>
+using namespace std;
+void addEdge(vector<pair<int, int>> adj[], int u, int v, int w){
+adj[u].push_back({v, w});
+}
+void dfsrec(vector<pair<int, int>> adj[], int V, int u, vector<bool> &visited){
+visited[u] = true;
+for(auto x : adj[u]){
+if(!visited[x.first])
+dfsrec(adj, V, x.first, visited);
+}
+cout << u << " ";
+}
+void dfs(vector<pair<int, int>> adj[], int V){
+vector<bool> visited(V, false);
+if(V <= 0)
+return;
+cout << endl;
+for(int i = 0; i < V; i++){
+if(!visited[i]){
+dfsrec(adj, V, i, visited);
+}
+} 
+cout << endl;
+}
+void indegree(vector<pair<int, int>> adj[], int V, vector<int> &indeg){
+for(int i = 0; i < V; i++){
+for(auto x : adj[i]){
+indeg[x.first]++;
+}
+}
+}
+void dfsrec(vector<pair<int, int>> adj[], int u, stack<int> &s, vector<bool> &visited){
+for(auto x : adj[u]){
+if(!visited[x.first])
+{
+visited[x.first] = true;
+dfsrec(adj, x.first, s, visited);
+}
+}
+s.push(u);
+}
+void rev(vector<pair<int, int>> adj[], vector<pair<int, int>> adjrev[], int V){
+for(int i = 0; i < V; i++){
+for(auto x : adj[i]){
+adjrev[x.first].push_back({i, 0});
+}
+}
+}
+int scc(vector<pair<int, int>> adj[], int V){
+stack<int> s;
+vector<bool> visited(V, false);
+for(int i = 0; i < V; i++){
+if(!visited[i]){
+visited[i] = true;
+dfsrec(adj, i, s, visited);
+}
+}
+//show(s);
+int c = 0;
+vector<pair<int, int>> adjrev[V]; 
+rev(adj, adjrev, V);
+vector<bool> visitedd(V, false);
+cout << "Strongly connected components are\n";
+while(!s.empty()){
+int u = s.top();
+s.pop();
+if(!visitedd[u]){
+dfsrec(adjrev, V, u, visitedd);
+cout << endl;
+c++;
+}
+}
+return c;
+}
+int main(){
+int V = 6;
+vector<pair<int, int>> adj[V];
+addEdge(adj, 0, 1, 10);
+addEdge(adj, 4, 2, 10);
+addEdge(adj, 4, 5, 30);
+addEdge(adj, 3, 4, 90);
+addEdge(adj, 2, 1, 10);
+addEdge(adj, 3, 5, 30);
+addEdge(adj, 1, 4, 90);
+addEdge(adj, 4, 0, 100);
+scc(adj, V);
+return 0;
+}