Graph algorithms

0Kosaraju.cpp

/**
 * Author : T Karthikeyan
**/

#include<iostream>
#include<bits/stdc++.h>
using namespace std;

void DFS(vector<int>adj[], int v); // finishing time
void DFSCC(vector<int>adjt[], int u); // printing SCC

vector<int>order;
int globalcounter = 0;
bool visited[100001] = {0}; // keep track of visited nodes

int main()
{
    //input graph
    int n, m;
    int u, v;
    cin >> n >> m;
    vector<int>adj[n+1]; // graph
    vector<int>adjt[n+1]; // transpose graph
    
    for(int i = 1; i <= m; i++)
    {
        cin >> u >> v;
        adj[u].push_back(v);
        adjt[v].push_back(u); 
    }

    // finish time

    for(int i = 1; i <= n; i++)
    {
        if(visited[i] == false)
            DFS(adj, i);
    }
    // re initialising visited array for further use
    for(int i = 1; i <= n; i++)
        visited[i] = false;

    // finding scc

    cout << endl;
    reverse(order.begin(), order.end());
    int K = 1;
    for(auto k = order.begin(); k!=order.end(); k++)
    {
        if(visited[*k] == false)
        {
            cout << "SCC "<< (K++)<< " : ";
            DFSCC(adjt, *k);
            cout << endl;
        }
    }
    
    return 0;
}

void DFS(vector<int>adj[], int v)
{
    visited[v] = true;

    for(int i = 0; i < adj[v].size(); i++)
    {
        int u = adj[v][i];
        if(visited[u])
            continue;
        visited[u] = true;
        DFS(adj, u);
    }
    order.push_back(v);
}

void DFSCC(vector<int>adjt[], int u)
{
    visited[u] = true;
    cout << u << " ";
    for(int i = 0; i < adjt[u].size(); i++)
    {
        int w = adjt[u][i];
        if(visited[w] == false)
            DFSCC(adjt, w);
    }
}

1input.txt

8 10
1 3
3 2
2 4
4 3
1 7
6 7
7 5
6 5
5 8
8 7

1output.txt

SCC 1 : 6
SCC 2 : 1
SCC 3 : 7 8 5
SCC 4 : 3 4 2