From db20df45e1f2d9de61b3b94433c0b0fa3b72aeec Mon Sep 17 00:00:00 2001
From: chaharnishant11 <nishantc.co.17@nsit.net.in>
Date: Tue, 14 Apr 2020 03:58:28 +0530
Subject: [PATCH] Strongly Connected Components

---
 .../SCC_kosaraju.cpp                          | 83 +++++++++++++++++++
 1 file changed, 83 insertions(+)
 create mode 100644 Competitive Coding/Graphs/Strongly Connected Components/SCC_kosaraju.cpp

diff --git a/Competitive Coding/Graphs/Strongly Connected Components/SCC_kosaraju.cpp b/Competitive Coding/Graphs/Strongly Connected Components/SCC_kosaraju.cpp
new file mode 100644
index 000000000..2dd1344c9
--- /dev/null
+++ b/Competitive Coding/Graphs/Strongly Connected Components/SCC_kosaraju.cpp	
@@ -0,0 +1,83 @@
+// { Driver Code Starts
+#include<bits/stdc++.h>
+using namespace std;
+// } Driver Code Ends
+
+/*  Function to find the number of strongly connected components
+*   using Kosaraju's algorithm
+*   V: number of vertices
+*   adj[]: array of vectors to represent graph
+*/
+void dfs1(vector<int> adj[],stack<int>& st,int s,bool* vis){
+    vis[s]=true;
+    for(auto j:adj[s]){
+        if(!vis[j]){
+            dfs1(adj,st,j,vis);
+        }
+    }
+    st.push(s);
+}
+void dfs2(vector<int> adj[],int s,bool* vis){
+    vis[s]=true;
+    for(auto j:adj[s]){
+        if(!vis[j]){
+            dfs2(adj,j,vis);
+        }
+    }
+}
+
+int kosaraju(int V, vector<int> adj[]){
+    // Your code here
+    bool vis[V];
+    for(int i=0;i<V;i++) vis[i]=false;
+    stack<int> st;
+    for(int i=0;i<V;i++){
+        if(!vis[i]){
+            dfs1(adj,st,i,vis);
+        }
+    }
+    vector<int> newg[V];
+    for(int i=0;i<V;i++){
+        vector<int> v;
+        newg[i]=v;
+    }
+    for(int i=0;i<V;i++){
+        for(auto j: adj[i]){
+            newg[j].push_back(i);
+        }
+    }
+    for(int i=0;i<V;i++) vis[i]=false;
+    int ans=0;
+    while(!st.empty()){
+        int t=st.top();
+        st.pop();
+        if(!vis[t]){
+            ans++;
+            dfs2(newg,t,vis);
+        }
+    }
+    return ans;
+}
+
+
+// { Driver Code Starts.
+
+int main()
+{ 
+    int t;
+    cin>>t;
+    while(t--)
+    {
+        int a,b ;
+   	    cin>>a>>b;
+   	    int m,n;
+   	    vector<int> adj[a+1];
+        for(int i=0;i<b;i++){
+            cin>>m>>n;
+            adj[m].push_back(n);
+        }
+        // exit(0);
+        cout<<kosaraju(a, adj)<<endl;
+    }
+    return 0;
+}  // } Driver Code Ends
\ No newline at end of file