Find given sequence is a valid topological sort or not

Detecting a valid topological sequence

Here given code implementation process.

//C program
//Find given sequence is a valid topological sort or not
#include <stdio.h>
#include <stdlib.h>

struct AjlistNode
{
  int vId;//Vertices id
  struct AjlistNode*next;
};

struct Graph
{
  int data; //node key value
  struct AjlistNode*next;
};

const int size=7; //number of nodes

//set node key value
void setData(struct Graph*node)
{
  if(node!=NULL && size>0)
  {
    int index=0;
    for(index;index<size;index++)
    {
      //set vertic node data
      node[index].data=index;//set node key
      //Initial no AjlistNode
      //set NULL Value
      node[index].next=NULL;
    }
  }
  else
  {
    printf("Vertices Node is Empty");
  }
}
//Add Edge from Two given Nodes
void addEdge(struct Graph*node, int V ,int E){
    //add edge form V to E
    //V and E is Node location
  if(V<size && E <size)
  {
    //first create Adjacency node
    struct AjlistNode *newEdge=(struct AjlistNode*)malloc(sizeof(struct AjlistNode));
    if(newEdge!=NULL)
    {

      newEdge->next=NULL;
      newEdge->vId=E;

      struct AjlistNode *temp=node[V].next;

      if(temp==NULL)
      {
        node[V].next=newEdge;
      }
      else
      {
        //Add node at last
        while(temp->next!=NULL)
        {
          temp=temp->next;
        }      
        temp->next=newEdge;          
      }
    }
    else
    {
      printf("\n Memory overflow");
    }
  }
  else
  {
    //not valid Vertices
    printf("Invalid Node Vertices %d  %d", V,E);
  }
}
//Find indegree of each nodes of a given graph
//Find the  incoming edges of each node
void findIndegree(int indegree[],struct Graph*node)
{

  if(node==NULL) return;

  struct AjlistNode *temp=NULL;

  for (int i = 0; i < size; ++i)
  {
    temp=node[i].next;

    while(temp!=NULL)
    {
      indegree[temp->vId]++;
      temp=temp->next;
    }
  }
}

//check the given  topological sequence is valid or not
void topological_find(struct Graph*node,int sequence[],int capacity)
{

  if(capacity!=size)
  {
    printf("Not Valid Topological Sequence\n" );
    return;
  }
  //store indegree of node edges
  int indegree[size];

  for(int i=0;i<size;i++)
  {
    //set initial zero
    indegree[i]=0;
  }

  //Find indegree of each node in graph
  findIndegree(indegree,node);

  printf("\n");
  
  int status=1;

  struct AjlistNode *edges=NULL;
  for (int i = 0; i < size; ++i)
  {
    //Compare to given sequence  into of indegree
    if(indegree[sequence[i]]==0 )
    {

      edges=node[sequence[i]].next;

      while(edges!=NULL)
      {
        indegree[edges->vId]--;
        edges=edges->next;
      }
    }
    else
    {
      status=0;
      break;
    }
  }
  //This is useful to compare given sequence are contain all elements or not, 
  //Assume that given sequence is a valid number of size
  for (int i = 0; i < size; ++i)
  {

    if(indegree[i]!=0)
    {
      status=0;
      break;
    }
  }
  for (int i = 0; i < size; ++i)
  {
    printf("%3d",sequence[i] );
  }
  printf("\n");
  if(status==0)
  {
    printf(" This is not a Valid Topological Sequence\n" );
    
  }
  else
  {
    printf(" Is a Valid Topological Sequence\n" );
  }

}

//Display Adjacency list of vertex
void printGraph(struct Graph*node)
{
  if(node!=NULL)
  {
    struct AjlistNode *temp=NULL;
    for(int index=0;index<size;index++)
    {
      printf("\n Adjacency list of vertex %d  :",index);
      temp=node[index].next;
      while(temp!=NULL)
      {
        //temp->vId is graph node vertices
        //In this case temp->vId is same as 
        //node[temp->vId].data

        printf("  %d",node[temp->vId].data);
        temp=temp->next;
      }
    }
  }
  else
  {
    printf("Empty Graph");
  }
}
int main()
{

  struct Graph*node=NULL;
  node=(struct Graph*)malloc(sizeof(struct Graph)*size);

  if(node==NULL)
  {
    printf("\n Memory overflow");
  }
  else
  {
    //First set node keys
    setData(node); 
    //Connected two node with Edges
    addEdge(node,0, 3);
    addEdge(node,0, 6);
    addEdge(node,2, 1);
    addEdge(node,2, 4);
    addEdge(node,3, 2); 
    addEdge(node,4, 1);
    addEdge(node,5, 2); 
    addEdge(node,5, 4); 
    addEdge(node,5, 6); 
    addEdge(node,6, 2);

    printGraph(node);

    
    int seq1[] = {0,3,5,6,2,4,1};
    int capacity=sizeof(seq1)/sizeof(seq1[0]);
    topological_find(node,seq1,capacity);

    int seq2[] = {5,0,6,3,2,1,4};
    capacity=sizeof(seq2)/sizeof(seq2[0]);
    topological_find(node,seq2,capacity);

    int seq3[] = {5,0,6,3,2,4,1};
    capacity=sizeof(seq3)/sizeof(seq3[0]);
    topological_find(node,seq3,capacity);
  }  
  return 0;
}

Output

 Adjacency list of vertex 0  :  3  6
 Adjacency list of vertex 1  :
 Adjacency list of vertex 2  :  1  4
 Adjacency list of vertex 3  :  2
 Adjacency list of vertex 4  :  1
 Adjacency list of vertex 5  :  2  4  6
 Adjacency list of vertex 6  :  2
  0  3  5  6  2  4  1
 Is a Valid Topological Sequence

  5  0  6  3  2  1  4
 This is not a Valid Topological Sequence

  5  0  6  3  2  4  1
 Is a Valid Topological Sequence

//C++ program
//Find given sequence is a valid topological sort or not

#include <iostream>
using namespace std;

struct AjlistNode
{
  int id;//Vertices id
  struct AjlistNode*next;
};

struct Vertices
{
  int data; //node key value
  struct AjlistNode*next;
};

class Graph
{
  Vertices *node;
  int size;//number of 
public:
  Graph(int);
  void set_data();
  void add_edge(int,int);
  void print_graph();
  void connect(int ,int );
  void topological_find(int sequence[],int capacity);
  void  find_indegree(int indegree[]);
};
Graph::Graph(int size)
{
  this->size = size;
  //set number of nodes
  node = new Vertices[size];
}
//set node key value
void Graph:: set_data()
{
  if(node!=NULL)
  {
    int index=0;

    for(index;index<size;index++)
    {
      //set vertic node data
      node[index].data=index;//set node key
      //Initial no AjlistNode
      //set NULL Value
      node[index].next=NULL;
    }
  }
  else
  {
    cout<<"Vertic Node is Empty"<<endl;
  }
}
//Add Edge from Two given Nodes
void Graph:: connect(int V ,int E)
{
    //add edge form V to E
    //V and E is Node location
    //first create Adjacency node
  AjlistNode *newEdge=new AjlistNode;

  if(newEdge!=NULL)
  {

    newEdge->next=NULL;
    newEdge->id=E;

    AjlistNode *temp=node[V].next;

    if(temp==NULL)
    {
      node[V].next=newEdge;
    }else
    {
            //Add node at last
      while(temp->next!=NULL)
      {
        temp=temp->next;
      }      
      temp->next=newEdge;          
    }
  }

}

void Graph:: add_edge(int V ,int E)
{
    //add edge form V to E
    //V and E is Node location
  if(V<size && E <size)
  {
    connect(V,E);

  }else
  {
        //not valid Vertices
    cout<<"Invalid Node Vertices "<< V<<" "<<E;
  }
}
//Display Adjacency list of vertex
void Graph:: print_graph()
{
  if(node!=NULL)
  {
    AjlistNode *temp=NULL;
    for(int index=0; index < size; index++)
    {
      cout<<"\n Adjacency list of vertex "<<index<<" :";
      temp=node[index].next;
      while(temp!=NULL)
      {
        //temp->id is graph node vertices
        //in this case temp->id is same as 
        //node[temp->id].data

        cout<<" "<<node[temp->id].data;
        temp=temp->next;
      }
    }
  }else
  {
    cout<<"Empty Graph"<<endl;
  }
}
//Find indegree of each nodes of a given graph
//Find the  incoming edges of each node
void Graph:: find_indegree(int indegree[])
{
  if (node==NULL) return ;
   AjlistNode *temp=NULL;
  for (int i = 0; i < size; ++i)
  {
    temp=node[i].next;
    while (temp!=NULL)
    {
      indegree[temp->id]++;
      temp=temp->next;
    }
  }
}


//check the given  topological sequence is valid or not
void Graph:: topological_find(int sequence[],int capacity)
{
  if(capacity!=size)
  {
    cout<<("Not Valid Topological Sequence\n" );
    return ;
  }
  //store indegree of node edges
  int indegree[size];
  for (int i=0;i<size;i++)
  {
    //set initial zero
    indegree[i]=0;
  }
  //Find indegree of each node in graph
  find_indegree(indegree);
  cout<<("\n");
  
  int status=1;
   AjlistNode *edges=NULL;
  for (int i = 0; i < size; ++i)
  {
    //Compare to given sequence  into of indegree
    if (indegree[sequence[i]]==0 )
    {
      edges=node[sequence[i]].next;
      while (edges!=NULL)
      {
        indegree[edges->id]--;
        edges=edges->next;
      }
    }
    else
    {
      status=0;
      break ;
    }
  }
  //This is useful to compare given sequence are contain all elements or not, 
  //Assume that given sequence is a valid number of size
  for (int i = 0; i < size; ++i)
  {
    if (indegree[i]!=0)
    {
      status=0;
      break ;
    }
  }
  for (int i = 0; i < size; ++i)
  {
    cout<<"  "<<sequence[i];
  }
  cout<<"\n";
  if (status==0)
  {
    cout<<(" This is not a Valid Topological Sequence\n" );
    
  }
  else
  {
    cout<<(" Is a Valid Topological Sequence\n" );
  }
}



int main()
{
  //Create Object
  Graph g = Graph(7);
  //First set node keys
  g.set_data();



  //Connected two node with Edges
  g.add_edge(0, 3);
  g.add_edge(0, 6);
  g.add_edge(2, 1);
  g.add_edge(2, 4);
  g.add_edge(3, 2); 
  g.add_edge(4, 1);
  g.add_edge(5, 2); 
  g.add_edge(5, 4); 
  g.add_edge(5, 6); 
  g.add_edge(6, 2);

  g.print_graph();

  
  int seq1[] = {0,3,5,6,2,4,1};
  int capacity=sizeof(seq1)/sizeof(seq1[0]);
  g.topological_find(seq1,capacity);

  int seq2[] = {5,0,6,3,2,1,4};
  capacity=sizeof(seq2)/sizeof(seq2[0]);
  g.topological_find(seq2,capacity);

  int seq3[] = {5,0,6,3,2,4,1};
  capacity=sizeof(seq3)/sizeof(seq3[0]);
  g.topological_find(seq3,capacity);



  return 0;
}

Output

 Adjacency list of vertex 0 : 3 6
 Adjacency list of vertex 1 :
 Adjacency list of vertex 2 : 1 4
 Adjacency list of vertex 3 : 2
 Adjacency list of vertex 4 : 1
 Adjacency list of vertex 5 : 2 4 6
 Adjacency list of vertex 6 : 2
  0  3  5  6  2  4  1
 Is a Valid Topological Sequence

  5  0  6  3  2  1  4
 This is not a Valid Topological Sequence

  5  0  6  3  2  4  1
 Is a Valid Topological Sequence
//Java program
//Find given sequence is a valid topological sort or not
public class MyGraph
{

  static class AjlistNode
  {
    int id;//Vertices node key
    AjlistNode next;
  }
  static class Vertices
  {
    int data;
    AjlistNode next;
  }

  //number of Vertices
  public  int size;
  public Vertices []node;

  MyGraph(int size)
  {
        //set value
    this.size = size;
 
    node = new Vertices[size];

  }

    //set initial node value
  public void set_data()
  {
    if(node == null)
    {
      System.out.println("\nEmpty Graph");
    }else
    {
      for(int index = 0; index < size; index++)
      {
                // avoid java.lang.nullPointerException
        node[index]=new Vertices(); 
        node[index].data=index;//set your data
        node[index].next=null;
      }
    }
  }
    //connect two nodes
  public void connect(int start,int end)
  {
    AjlistNode newEdge=new AjlistNode();
    newEdge.id=end;//end node
    newEdge.next=null;
    if(node[start].next==null)
    {
      node[start].next=newEdge;
    }else
    {
      AjlistNode temp=node[start].next;

      while(temp.next!=null)
      {
        temp=temp.next;
      }
      temp.next=newEdge;
    }
  }
    //Add edge at the end
  public void add_edge(int start,int end)
  {
    if(start < size && end < size && node != null)
    {
      connect(start,end);

    }
    else{
      System.out.println("\nInvalid nodes "+start+" "+end);
    }
  }

  public void print_graph()
  {

    if(size>0 && node!=null)
    {
      for(int index=0;index<size;index++)
      {
        System.out.print("\nAdjacency list of vertex "+index+" :");

        AjlistNode temp=node[index].next;

        while(temp!=null)
        {
          System.out.print(" "+node[temp.id].data);

          temp=temp.next;
        }
      }
    }
  }

//Find indegree of each nodes of a given graph
//Find the  incoming edges of each node
public void  find_indegree(int indegree[])
{
  if (node==null) return ;
   AjlistNode  temp=null;
  for (int i = 0; i < size; ++i)
  {
    temp=node[i].next;
    while (temp!=null)
    {
      indegree[temp.id]++;
      temp=temp.next;
    }
  }
}


//check the given  topological sequence is valid or not
public void topological_find(int []sequence,int capacity)
{
  if(capacity!=size)
  {
    System.out.print("Not Valid Topological Sequence\n");
    return ;
  }
  //store indegree of node edges
  int []indegree=new int[size];
  for (int i=0;i<size;i++)
  {
    //set initial zero
    indegree[i]=0;
  }
  //Find indegree of each node in graph
  find_indegree(indegree);
  System.out.print("\n");
  
  int status=1;
  AjlistNode  edges=null;
  for (int i = 0; i < size; ++i)
  {
    //Compare to given sequence  into of indegree
    if (indegree[sequence[i]]==0 )
    {
      edges=node[sequence[i]].next;
      while (edges!=null)
      {
        indegree[edges.id]--;
        edges=edges.next;
      }
    }
    else
    {
      status=0;
      break ;
    }
  }
  //This is useful to compare given sequence are contain all elements or not, 
  //Assume that given sequence is a valid number of size
  for (int i = 0; i < size; ++i)
  {
    if (indegree[i]!=0)
    {
      status=0;
      break ;
    }
  }
  for (int i = 0; i < size; ++i)
  {
    System.out.print("  "+sequence[i]);
  }
  System.out.print("\n");
  if (status==0)
  {
    System.out.print(" This is not a Valid Topological Sequence\n" );
    
  }
  else
  {
    System.out.print(" Is a Valid Topological Sequence\n" );
  }
}

  public static void main(String[] args) 
  {
    int totalNode=7;

    MyGraph g=new MyGraph(totalNode);
    g.set_data();
     //Connected two node with Edges
    g.add_edge(0, 3);
    g.add_edge(0, 6);
    g.add_edge(2, 1);
    g.add_edge(2, 4);
    g.add_edge(3, 2); 
    g.add_edge(4, 1);
    g.add_edge(5, 2); 
    g.add_edge(5, 4); 
    g.add_edge(5, 6); 
    g.add_edge(6, 2);

    g.print_graph();


    int []seq1 = new int[]{0,3,5,6,2,4,1};
    int capacity=seq1.length;
    g.topological_find(seq1,capacity);

    int []seq2 = new int[]{5,0,6,3,2,1,4};
    capacity=seq2.length;
    g.topological_find(seq2,capacity);

    int []seq3 = new int[]{5,0,6,3,2,4,1};
    capacity=seq3.length;
    g.topological_find(seq3,capacity);
  }
}

Output

Adjacency list of vertex 0 : 3 6
Adjacency list of vertex 1 :
Adjacency list of vertex 2 : 1 4
Adjacency list of vertex 3 : 2
Adjacency list of vertex 4 : 1
Adjacency list of vertex 5 : 2 4 6
Adjacency list of vertex 6 : 2
  0  3  5  6  2  4  1
 Is a Valid Topological Sequence

  5  0  6  3  2  1  4
 This is not a Valid Topological Sequence

  5  0  6  3  2  4  1
 Is a Valid Topological Sequence
#Python program
#Find given sequence is a valid topological sort or not

class AjLinkeNode:
  def __init__(self,data):
    self.key=data
    self.next=None

class Vertices:
  def __init__(self,data):
    self.data=data
    self.next=None

class Graph:

  def __init__(self,size):
    self.size=size
    self.node=[]
    

  def set_data(self):
    if(self.size>0 and self.node!=None):
      index=0
      while(index<self.size):
        self.node.append(Vertices(index))
        index+=1


  #connect two node with  edge
  def connect(self,start,end):
    new_edge=AjLinkeNode(end)
    if(self.node[start].next==None):
      self.node[start].next=new_edge
    else:
      temp=self.node[start].next
      while(temp.next!=None):
        temp=temp.next
      temp.next=new_edge  

  #add edge
  def add_edge(self,start,end):

    #start,end is two nodes
    if(self.size>start and self.size>start):
      
      self.connect(start,end)
  
    else:
      print("Invalid nodes")


  def print_graph(self):

    if(self.size>0 and self.node!=None):

      index=0

      while(index<self.size):

        print("\nAdjacency list of vertex  {0} :".format(index),end=" ")
        
        temp=self.node[index].next
        
        while temp!=None:

          print(" {0}".format(temp.key),end=" ")

          temp=temp.next

        index+=1

  

  
  #Find indegree of each nodes of a given graph
  #Find the  incoming edges of each node
  def find_indegree(self,indegree) :

    if (self.node==None) :

      return 
    temp=None
    i = 0
    while ( i < self.size ) :

      temp=self.node[i].next
      while (temp!=None) :

        indegree[temp.key] += 1
        temp=temp.next
      i+=1
  #check the given  topological sequence is valkey or not
  def  topological_find(self,sequence, capacity) :

    if(capacity!=self.size) :

      print("Not Valid Topological Sequence\n")

      return 
    #store indegree of node edges
    indegree=[False]*self.size
    #Find indegree of each node in graph
    self.find_indegree(indegree)
    print("\n")

    status=1
    edges=None
    i = 0
    while (  i < self.size ) :

      #Compare to given sequence  into of indegree
      if (indegree[sequence[i]]==False ) :

        edges=self.node[sequence[i]].next
        while (edges!=None) :

          indegree[edges.key] -=1 
          edges=edges.next
      else :

        status=0
        break 
      i+=1
    

    i = 0  
    #This is useful to compare given sequence are contain all elements or not,
    #Assume that given sequence is a valkey number of size
    while ( i < self.size ) :

      if (indegree[i]!=False) :
        status=0
        break 

      i+=1

    i = 0
    while ( i < self.size) :

      print(sequence[i],end=" ")
      i+=1
    

    if(status==0) :

      print("\n This is not a Valid Topological Sequence")

    else :

      print("\n Is a Valid Topological Sequence")


def main():
  g=Graph(7)

  g.set_data();
  #Connected two node with Edges
  g.add_edge(0, 3)
  g.add_edge(0, 6)
  g.add_edge(2, 1)
  g.add_edge(2, 4)
  g.add_edge(3, 2) 
  g.add_edge(4, 1)
  g.add_edge(5, 2) 
  g.add_edge(5, 4) 
  g.add_edge(5, 6) 
  g.add_edge(6, 2)
  g.print_graph()
  seq1 =[0,3,5,6,2,4,1]
  capacity=len(seq1)
  g.topological_find(seq1,capacity)
  seq2 = [5,0,6,3,2,1,4]
  capacity=len(seq2)
  g.topological_find(seq2,capacity)
  seq3 = [5,0,6,3,2,4,1]
  capacity=len(seq3)
  g.topological_find(seq3,capacity)

if __name__=="__main__":
    main()

Output

Adjacency list of vertex  0 :  3  6 
Adjacency list of vertex  1 : 
Adjacency list of vertex  2 :  1  4 
Adjacency list of vertex  3 :  2 
Adjacency list of vertex  4 :  1 
Adjacency list of vertex  5 :  2  4  6 
Adjacency list of vertex  6 :  2 

0 3 5 6 2 4 1 
 Is a Valid Topological Sequence


5 0 6 3 2 1 4 
 This is not a Valid Topological Sequence


5 0 6 3 2 4 1 
 Is a Valid Topological Sequence
//C# program
//Find given sequence is a valid topological sort or not
using System;
public class AjlistNode
{
  public int id;//Vertices node key
  public AjlistNode next;
}
public class Vertices
{
  public int data;
  public AjlistNode next;
}
public class MyGraph
{

  //number of Vertices
  public  int size;
  public Vertices []node;

  MyGraph(int size)
  {
    //set value
    this.size = size;

    node = new Vertices[size];

  }

  //set initial node value
  public void set_data()
  {
    if(node == null)
    {
      Console.WriteLine("\nEmpty Graph");
    }else
    {
      for(int index = 0; index < size; index++)
      {
        // avoid C#.lang.nullPointerException
        node[index]=new Vertices(); 
        node[index].data=index;//set your data
        node[index].next=null;
      }
    }
  }
  //connect two nodes
  public void connect(int start,int end)
  {
    AjlistNode newEdge=new AjlistNode();
    newEdge.id=end;//end node
    newEdge.next=null;
    if(node[start].next==null)
    {
      node[start].next=newEdge;
    }else
    {
      AjlistNode temp=node[start].next;

      while(temp.next!=null)
      {
        temp=temp.next;
      }
      temp.next=newEdge;
    }
  }
  //Add edge at the end
  public void add_edge(int start,int end)
  {
    if(start < size && end < size && node != null)
    {
      connect(start,end);

    }
    else{
      Console.WriteLine("\nInvalid nodes "+start+" "+end);
    }
  }

  public void print_graph()
  {

    if(size>0 && node!=null)
    {
      for(int index=0;index<size;index++)
      {
        Console.Write("\nAdjacency list of vertex "+index+" :");

        AjlistNode temp=node[index].next;

        while(temp!=null)
        {
          Console.Write(" "+node[temp.id].data);

          temp=temp.next;
        }
      }
    }
  }

  //Find indegree of each nodes of a given graph
  //Find the  incoming edges of each node
  public void  find_indegree(int []indegree)
  {
    if (node==null) return ;
    AjlistNode  temp=null;
    for (int i = 0; i < size; ++i)
    {
      temp=node[i].next;
      while (temp!=null)
      {
        indegree[temp.id]++;
        temp=temp.next;
      }
    }
  }


  //check the given  topological sequence is valid or not
  public void topological_find(int []sequence,int capacity)
  {
    if(capacity!=size)
    {
      Console.Write("Not Valid Topological Sequence\n");
      return ;
    }
    //store indegree of node edges
    int []indegree=new int[size];
    for (int i=0;i<size;i++)
    {
      //set initial zero
      indegree[i]=0;
    }
    //Find indegree of each node in graph
    find_indegree(indegree);
    Console.Write("\n");

    int status=1;
    AjlistNode  edges=null;
    for (int i = 0; i < size; ++i)
    {
      //Compare to given sequence  into of indegree
      if (indegree[sequence[i]]==0 )
      {
        edges=node[sequence[i]].next;
        while (edges!=null)
        {
          indegree[edges.id]--;
          edges=edges.next;
        }
      }
      else
      {
        status=0;
        break ;
      }
    }
    //This is useful to compare given sequence are contain all elements or not, 
    //Assume that given sequence is a valid number of size
    for (int i = 0; i < size; ++i)
    {
      if (indegree[i]!=0)
      {
        status=0;
        break ;
      }
    }
    for (int i = 0; i < size; ++i)
    {
      Console.Write("  "+sequence[i]);
    }
    Console.Write("\n");
    if (status==0)
    {
      Console.Write(" This is not a Valid Topological Sequence\n" );

    }
    else
    {
      Console.Write(" Is a Valid Topological Sequence\n" );
    }
  }

  public static void Main(String[] args) 
  {
    int totalNode=7;

    MyGraph g=new MyGraph(totalNode);
    g.set_data();
    //Connected two node with Edges
    g.add_edge(0, 3);
    g.add_edge(0, 6);
    g.add_edge(2, 1);
    g.add_edge(2, 4);
    g.add_edge(3, 2); 
    g.add_edge(4, 1);
    g.add_edge(5, 2); 
    g.add_edge(5, 4); 
    g.add_edge(5, 6); 
    g.add_edge(6, 2);

    g.print_graph();


    int []seq1 = new int[]{0,3,5,6,2,4,1};
    int capacity=seq1.Length;
    g.topological_find(seq1,capacity);

    int []seq2 = new int[]{5,0,6,3,2,1,4};
    capacity=seq2.Length;
    g.topological_find(seq2,capacity);

    int []seq3 = new int[]{5,0,6,3,2,4,1};
    capacity=seq3.Length;
    g.topological_find(seq3,capacity);
  }
}

Output

Adjacency list of vertex 0 : 3 6
Adjacency list of vertex 1 :
Adjacency list of vertex 2 : 1 4
Adjacency list of vertex 3 : 2
Adjacency list of vertex 4 : 1
Adjacency list of vertex 5 : 2 4 6
Adjacency list of vertex 6 : 2
  0  3  5  6  2  4  1
 Is a Valid Topological Sequence

  5  0  6  3  2  1  4
 This is not a Valid Topological Sequence

  5  0  6  3  2  4  1
 Is a Valid Topological Sequence
<?php 
/*
* PHP Program 
* Find given sequence is a valkey topological sort or not
*/

class AjlistNode
{
  public $key;
  public $next;
  function __construct($key)
  {
    $this->key=$key;
    $this->next=NULL;
  }
}

class Node
{
  public $data;
  public $next;
  function __construct($data)
  {
    $this->data=$data;
    $this->next=NULL;

  }
}
class MyGraph
{

  public $node;
  public $size;
  function __construct($size)
  {
    $this->size=$size;
    $this->node=[];  //empty array

  }
  public function set_data()
  {
    if($this->size>0)
    {
      for($index=0;$index<$this->size;$index++)
      {
        $this->node[$index]=new Node($index);
      }

    }
  }
  public function connect($start,$end)
  {
    $newEdge=new AjlistNode($end);
    if($this->node[$start]->next==NULL)
    {
      $this->node[$start]->next=$newEdge;
    }
    else
    {
      $temp=$this->node[$start]->next;
      while($temp->next!=NULL)
      {
        $temp=$temp->next;
      }
      $temp->next= $newEdge;
    }
  }
  public function add_edge($start,$end)
  {
    if($this->size > $start && $this->size>$end)
    {
      $this->connect($start,$end);
    }
    else
    {
      echo "\n Invalkey node";
    }
  }
  public function print_graph()
  {
    if($this->size>0 && count($this->node)>0 && $this->node!=NULL)
    {
      for($index=0;$index<$this->size;$index++)
      {
        echo "\nAdjacency list of vertex ".$index." : ";

        $temp=$this->node[$index]->next;

        while($temp!=NULL)
        {
          echo "  ".$this->node[$temp->key]->data;
          $temp=$temp->next;
        }
      }
    }
  }
  //Find indegree of each nodes of a given graph
  //Find the  incoming edges of each node
  public function  find_indegree( &$indegree=array())
  {
    if ($this->node==NULL)
    {
      return ;
    }
    $temp=NULL;
    for ( $i = 0; $i < $this->size; ++$i)
    {
      $temp=$this->node[$i]->next;
      while ($temp!=NULL)
      {
        $indegree[$temp->key]++;
        $temp=$temp->next;
      }
    }
  }


  //check the given  topological sequence is valkey or not
  public function topological_find( &$sequence, $capacity)
  {
    if($capacity!=$this->size)
    {
      echo "Not Valkey Topological Sequence\n";
      return ;
    }
    //store indegree of node edges
    $indegree=array_fill(0, $this->size, False);

    //Find indegree of each node in graph
    $this->find_indegree($indegree);
    echo "\n";
    
    $status=1;
    $edges=NULL;
    for ( $i = 0; $i < $this->size; ++$i)
    {
      //Compare to given sequence  into of indegree
      if ($indegree[$sequence[$i]]==False )
      {
        $edges=$this->node[$sequence[$i]]->next;
        while ($edges!=NULL)
        {
          $indegree[$edges->key]--;
          $edges=$edges->next;
        }
      }
      else
      {
        $status=0;
        break ;
      }
    }
    //This is useful to compare given sequence are contain all elements or not, 
    //Assume that given sequence is a valkey number of size
    for ( $i = 0; $i < $this->size; ++$i)
    {
      if ($indegree[$i]!=False)
      {
        $status=0;
        break ;
      }
    }
    for ($i = 0; $i < $this->size; ++$i)
    {
      echo "  ".$sequence[$i];
    }
    echo "\n";
    if($status==0)
    {
      echo " This is not a Valkey Topological Sequence\n";
      
    }
    else
    {
      echo " Is a Valkey Topological Sequence\n";
    }
  }
}


function main()
{
  //create object
  $g=new MyGraph(7);
  //First set node keys
  $g->set_data();

  //Connected two node with Edges
  $g->add_edge(0, 3);
  $g->add_edge(0, 6);
  $g->add_edge(2, 1);
  $g->add_edge(2, 4);
  $g->add_edge(3, 2); 
  $g->add_edge(4, 1);
  $g->add_edge(5, 2); 
  $g->add_edge(5, 4); 
  $g->add_edge(5, 6); 
  $g->add_edge(6, 2);

  $g->print_graph();

  
  $seq1 = array(0,3,5,6,2,4,1);
  $capacity=count($seq1);
  $g->topological_find($seq1,$capacity);

  $seq2 = array(5,0,6,3,2,1,4);
  $capacity=count($seq2);
  $g->topological_find($seq2,$capacity);

  $seq3 = array(5,0,6,3,2,4,1);
  $capacity=count($seq3);
  $g->topological_find($seq3,$capacity);


}
main();
?>

Output

Adjacency list of vertex 0 :   3  6
Adjacency list of vertex 1 : 
Adjacency list of vertex 2 :   1  4
Adjacency list of vertex 3 :   2
Adjacency list of vertex 4 :   1
Adjacency list of vertex 5 :   2  4  6
Adjacency list of vertex 6 :   2
  0  3  5  6  2  4  1
 Is a Valkey Topological Sequence

  5  0  6  3  2  1  4
 Is a Valkey Topological Sequence

  5  0  6  3  2  4  1
 Is a Valkey Topological Sequence

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