1 // A C++ program to print topological
2 // sorting of a DAG
3 #include <iostream>
4 #include <list>
5 #include <stack>
6 using namespace std;
7
8 // Class to represent a graph
9 class Graph {
10 // No. of vertices'
11 int V;
12
13 // Pointer to an array containing adjacency listsList
14 list<int>* adj;
15
16 // A function used by topologicalSort
17 void topologicalSortUtil(int v, bool visited[],
18 stack<int>& Stack);
19
20 public:
21 // Constructor
22 Graph(int V);
23
24 // function to add an edge to graph
25 void addEdge(int v, int w);
26
27 // prints a Topological Sort of
28 // the complete graph
29 void topologicalSort();
30 };
31
32 Graph::Graph(int V)
33 {
34 this->V = V;
35 adj = new list<int>[V];
36 }
37
38 void Graph::addEdge(int v, int w)
39 {
40 // Add w to v’s list.
41 adj[v].push_back(w);
42 }
43
44 // A recursive function used by topologicalSort
45 void Graph::topologicalSortUtil(int v, bool visited[],
46 stack<int>& Stack)
47 {
48 // Mark the current node as visited.
49 visited[v] = true;
50
51 // Recur for all the vertices
52 // adjacent to this vertex
53 list<int>::iterator i;
54 for (i = adj[v].begin(); i != adj[v].end(); ++i)
55 if (!visited[*i])
56 topologicalSortUtil(*i, visited, Stack);
57
58 // Push current vertex to stack
59 // which stores result
60 Stack.push(v);
61 }
62
63 // The function to do Topological Sort.
64 // It uses recursive topologicalSortUtil()
65 void Graph::topologicalSort()
66 {
67 stack<int> Stack;
68
69 // Mark all the vertices as not visited
70 bool* visited = new bool[V];
71 for (int i = 0; i < V; i++)
72 visited[i] = false;
73
74 // Call the recursive helper function
75 // to store Topological
76 // Sort starting from all
77 // vertices one by one
78 for (int i = 0; i < V; i++)
79 if (visited[i] == false)
80 topologicalSortUtil(i, visited, Stack);
81
82 // Print contents of stack
83 while (Stack.empty() == false) {
84 cout << Stack.top() << " ";
85 Stack.pop();
86 }
87 }
88
89 // Driver Code
90 int main()
91 {
92 // Create a graph given in the above diagram
93 Graph g(6);
94 g.addEdge(5, 2);
95 g.addEdge(5, 0);
96 g.addEdge(4, 0);
97 g.addEdge(4, 1);
98 g.addEdge(2, 3);
99 g.addEdge(3, 1);
100
101 cout << "Following is a Topological Sort of the given "
102 "graph \n";
103
104 // Function Call
105 g.topologicalSort();
106
107 return 0;
108 }
![](https://img2020.cnblogs.com/blog/1409275/202108/1409275-20210829015217052-1194965607.png)