Topological sort
Program to print in topological order and verify that given compilation order correctness based on the dependency of files :
// A C++ program to print topological sorting of a Directd Acyclic //Graph
#include<iostream>
#include <list>
#include <stack>
#include <algorithm>
using namespace std;
// Class to represent a graph
class Graph
{
int V; // No. of vertices’
// Pointer to an array containing adjacency listsList
list<int> *adj;
// A function used by topologicalSort
void topologicalSortUtil(int v, bool visited[], stack<int> &Stack);
public:
Graph(int V); // Constructor
// function to add an edge to graph
void addEdge(int v, int w);
// prints a Topological Sort of the complete graph
void topologicalSort();
bool edgeExist(int s, int d);
bool isFollowingOrderAllowed( int *arr, int size);
};
Graph::Graph(int V)
{
this->V = V;
adj = new list<int>[V];
}
void Graph::addEdge(int v, int w)
{
adj[v].push_back(w); // Add w to v’s list.
}
// A recursive function used by topologicalSort
void Graph::topologicalSortUtil(int v, bool visited[],
stack<int> &Stack)
{
// Mark the current node as visited.
visited[v] = true;
// Recur for all the vertices adjacent to this vertex
list<int>::iterator i;
for (i = adj[v].begin(); i != adj[v].end(); ++i)
if (!visited[*i])
topologicalSortUtil(*i, visited, Stack);
// Push current vertex to stack which stores result
Stack.push(v);
}
// The function to do Topological Sort. It uses recursive
// topologicalSortUtil()
void Graph::topologicalSort()
{
stack<int> Stack;
// Mark all the vertices as not visited
bool *visited = new bool[V];
for (int i = 0; i < V; i++)
visited[i] = false;
// Call the recursive helper function to store Topological
// Sort starting from all vertices one by one
for (int i = 0; i < V; i++)
if (visited[i] == false)
topologicalSortUtil(i, visited, Stack);
// Print contents of stack
while (Stack.empty() == false)
{
cout << Stack.top() << ” “;
Stack.pop();
}
}
bool Graph::edgeExist(int s, int d)
{
std::list<int>::iterator result = adj[s].begin();
result = std::find( result, adj[s].end(),d );
if (result == adj[s].end()) return 0;
return 1;
}
bool Graph::
{
list<int>::iterator i;
for (i = adj[4].begin(); i != adj[4].end(); ++i)
cout << *i << “\t” ;
for(int i = 0 ; i < size-1 ; i++)
{
if(! edgeExist(arr[i] , arr[i+1]))
return 0 ;
}
return 1 ;
}
// Driver program to test above functions
int main()
{
// Create a graph given in the above diagram
Graph g(6);
g.addEdge(5, 2);
g.addEdge(5, 0);
g.addEdge(4, 0);
g.addEdge(4, 1);
g.addEdge(2, 3);
g.addEdge(3, 1);
cout << “Following is a Topological Sort of the given graph \n”;
g.topologicalSort();
int arr[5] = {5,2,3};
cout << endl << g.isFollowingOrderAllowed(arr,
return 0;
}
