Kết nối yếu hoặc mạnh cho một đồ thị có hướng nhất định có thể được tìm hiểu bằng cách sử dụng DFS. Đây là một chương trình C ++ cho vấn đề này.
Các hàm được sử dụng
Begin Function fillorder() = fill stack with all the vertices. a) Mark the current node as visited and print it b) Recur for all the vertices adjacent to this vertex c) All vertices reachable from v are processed by now, push v to Stack End Begin Function DFS() : a) Mark the current node as visited and print it b) Recur for all the vertices adjacent to this vertex End
Ví dụ
#include <iostream>
#include <list>
#include <stack>
using namespace std;
class G {
int m;
list<int> *adj;
//declaration of functions
void fillOrder(int n, bool visited[], stack<int> &Stack);
void DFS(int n, bool visited[]);
public:
G(int N); //constructor
void addEd(int v, int w);
int print();
G getTranspose();
};
G::G(int m) {
this->m = m;
adj = new list<int> [m];
}
void G::DFS(int n, bool visited[]) {
visited[n] = true; // Mark the current node as visited and print it
cout << n << " ";
list<int>::iterator i;
//Recur for all the vertices adjacent to this vertex
for (i = adj[n].begin(); i != adj[n].end(); ++i)
if (!visited[*i])
DFS(*i, visited);
}
G G::getTranspose() {
G g(m);
for (int n = 0; n< m; n++) {
list<int>::iterator i;
for (i = adj[n].begin(); i != adj[n].end(); ++i) {
g.adj[*i].push_back(n);
}
}
return g;
}
void G::addEd(int v, int w) {
adj[v].push_back(w); //add w to v's list
}
void G::fillOrder(int v, bool visited[], stack<int> &Stack) {
visited[v] = true; //Mark the current node as visited and print it
list<int>::iterator i;
//Recur for all the vertices adjacent to this vertex
for (i = adj[v].begin(); i != adj[v].end(); ++i)
if (!visited[*i])
fillOrder(*i, visited, Stack);
Stack.push(v);
}
int G::print() //print the solution {
stack<int> Stack;
bool *visited = new bool[m];
for (int i = 0; i < m; i++)
visited[i] = false;
for (int i = 0; i < m; i++)
if (visited[i] == false)
fillOrder(i, visited, Stack);
G graph = getTranspose(); //Create a reversed graph
for (int i = 0; i < m; i++)//Mark all the vertices as not visited
visited[i] = false;
int count = 0;
//now process all vertices in order defined by Stack
while (Stack.empty() == false) {
int v = Stack.top();
Stack.pop(); //pop vertex from stack
if (visited[v] == false) {
graph.DFS(v, visited);
cout << endl;
}
count++;
}
return count;
}
int main() {
G g(5);
g.addEd(2, 1);
g.addEd(3, 2);
g.addEd(1, 0);
g.addEd(0, 3);
g.addEd(3, 1);
cout << "Following are strongly connected components in given graph \n";
if (g.print() > 1) {
cout << "Graph is weakly connected.";
} else {
cout << "Graph is strongly connected.";
}
return 0;
} Đầu ra
Following are strongly connected components in given graph 4 0 1 2 3 Graph is weakly connected.