Wednesday 22 November 2017

C++ Program for Topological Sorting in Graphs


Code:

#include    iostream
#include    conio.h
using namespace std;
struct node_info
{
    int no;
    int lv_time, st_time;
}*q = NULL, *r = NULL;
struct node
{
    node_info *pt;
    node *next;
}*top = NULL, *p = NULL, *np = NULL;
int c = 0;
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);
    }
}
void topo(int *v,int am[][7],int i)
{
    q = new node_info;
    q->no = i;
    q->st_time = c;
    cout<<"start time for node no "<no<<":"<
    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)
        {
            c++;
            topo(v,am,j);
        }
    }
    c++;
    r = pop();
    cout<<"leave time for "<no<<":"<
    return;
}
int main()
{
    int v[7],am[7][7];
    for (int i = 0; i < 7; i++)
    v[i] = 0;
    for (int i = 0; i < 7; i++)
    {
        cout<<"enter the values for adjacency matrix row:"<
        for(int j = 0; j < 7; j++)
        {
            cin>>am[i][j];
        }
    }
    topo(v,am,0);
    getch();
}


Output:

enter the values for adjacency matrix row:1
0
1
1
0
0
1
1
enter the values for adjacency matrix row:2
1
0
0
0
0
0
0
enter the values for adjacency matrix row:3
1
0
0
0
0
0
1
enter the values for adjacency matrix row:4
0
0
0
0
1
1
0
enter the values for adjacency matrix row:5
0
0
0
1
0
1
1
enter the values for adjacency matrix row:6
1
0
0
1
1
0
0
enter the values for adjacency matrix row:7
1
0
1
0
1
0
0
start time for node no 0:0
start time for node no 1:1
leave time for node no 1:2
start time for node no 2:3
start time for node no 6:4
start time for node no 4:5
start time for node no 3:6
start time for node no 5:7
leave time for node no 5:8
leave time for node no 3:9
leave time for node no 4:10
leave time for node no 6:11
leave time for node no 2:12
leave time for node no 0:13



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