C++ Program to Find Number of Articulation Points in a Graph

This C++ program displays the articulation points present inside a graph. An articulation point inside a graph is the vertex whose removal increases the number of connected components.

Here is the source code of the C++ program to display the nodes which are considered to be articulation points. This C++ program is successfully compiled and run on DevCpp, a C++ compiler.The program output is given below.

```
/*
```

 * C++ Program to Find Number of Articulation points in a Graph

```
 */
```
```
#include<iostream>
```
```
#include<conio.h>
```
```
using namespace std;
```
```
int cnt = 0;
```
```
struct node_info
```
```
{
```
```
    int no;
```
```
}*q = NULL, *r = NULL;
```
```
struct node
```
```
{
```
```
    node_info *pt;
```
```
    node *next;
```
```
}*top = NULL, *p = NULL, *np = NULL;
```
```
void push(node_info *ptr)
```
```
{
```
```
    np = new node;
```
```
    np->pt = ptr;
```
```
    np->next = NULL;
```
```
    if (top == NULL)
```
```
    {
```
```
        top = np;
```
```
    }
```
```
    else
```
```
    {
```
```
        np->next = top;
```
```
        top = np;
```
```
    }
```
```
}
```
```
node_info *pop()
```
```
{
```
```
    if (top == NULL)
```
```
    {
```
```
        cout<<"underflow\n";
```
```
    }
```
```
    else
```
```
    {
```
```
        p = top;
```
```
        top = top->next;
```
```
        return(p->pt);
```
```
        delete(p);
```
```
    }
```
```
}           
```
```
int topo(int *v, int am[][7], int i)
```
```
{
```
```
    q = new node_info;
```
```
    q->no = i;
```
```
    push(q);
```
```
    v[i] = 1;
```
```
    for (int j = 0; j < 7; j++)
```
```
    {
```

        if (am[i][j] == 0  || (am[i][j] == 1 && v[j] == 1))

```
            continue;
```

        else if(am[i][j] == 1 && v[j] == 0)

```
        {
```
```
            cnt++;
```
```
            topo(v, am, j);
```
```
        }
```
```
    }
```
```
    q = pop();
```
```
}
```

void addEdge(int am[][7], int src, int dest)

```
{
```
```
     am[src][dest] = 1;
```
```
     am[dest][src] = 1;
```
```
     return;
```
```
}
```
```
int main()
```
```
{
```

    int v[7], am[7][7], amt[7][7], c = 0, a, b, x = 0;

```
    for (int i = 0; i < 7; i++)
```
```
    {
```
```
        v[i] = 0;
```
```
    }
```
```
    for (int i = 0; i < 7; i++)
```
```
    {
```
```
        for (int j = 0; j < 7; j++)
```
```
        {
```
```
            am[i][j] = 0;
```
```
        }
```
```
    }
```
```
    while (c < 9)
```
```
    {
```

        cout<<"Enter the source and destination\n";

```
        cin>>a>>b;
```
```
        addEdge(am, a, b);
```
```
        c++;
```
```
    }
```
```
    for (int i = 0; i < 7; i++)
```
```
    {
```
```
        for (int j = 0; j < 7; j++)
```
```
        {
```
```
            amt[i][j] = am[i][j];
```
```
        }
```
```
    }
```
```
    for (int i = 0; i < 7; i++)
```
```
    {
```
```
        for(int j = 0; j < 7; j++)
```
```
        {
```
```
            am[i][j] = 0;
```
```
            am[j][i] = 0;
```
```
        }
```
```
        if (i < 6)
```
```
        {
```
```
            topo(v, am, i + 1);
```
```
        }
```
```
        else
```
```
        {
```
```
            topo(v, am, 0);
```
```
        }
```
```
        if (cnt < 5)
```
```
        {
```

            cout<<endl<<i<<" is an articulation point"<<endl;

```
        }
```
```
        cnt = 0;
```
```
        for (int j = 0; j < 7; j++)
```
```
        {
```
```
            am[i][j] = amt[i][j];
```
```
            am[j][i] = amt[j][i];
```
```
            v[j] = 0;
```
```
        }
```
```
        while (top != NULL)
```
```
        {
```
```
              pop();
```
```
        }
```
```
    }
```
```
    getch();
```
```
}
```

Output:
 
Enter the source and destination
0
1
Enter the source and destination
0
5
Enter the source and destination
5
4
Enter the source and destination
4
6
Enter the source and destination
0
6
Enter the source and destination
6
2
Enter the source and destination
2
0
Enter the source and destination
3
5
Enter the source and destination
4
3
 
0 is an articulation point

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