算法系列之图--拓扑排序

 1 #include <iostream>
 2 #include <list>
 3 #include <stack>
 4 using namespace std;
 5 
 6 //拓扑排序里的图应该是有向无环图
 7 class DAG{
 8 private:
 9     int v;
10     list<int> *adj;
11     void topologicalSortUtil(int v,bool *visited,stack<int>& Stack);
12 public:
13     DAG(int v);//ctor
14     void addEdge(int start,int end);//DAG中是有向图
15     void topologicalSort();
16 };
17 
18 DAG::DAG(int v){
19     this->v = v;
20     adj = new list<int>[v];
21 }
22 
23 void DAG::addEdge(int start,int end){
24     adj[start].push_back(end);
25 }
26 
27 void DAG::topologicalSortUtil(int v,bool* visited,stack<int>& Stack){
28     visited[v] = true;
29 
30     list<int>::iterator beg = adj[v].begin();
31     for (;beg != adj[v].end();++beg)
32         if (visited[*beg] == false)
33             topologicalSortUtil(*beg,visited,Stack);
34     Stack.push(v);
35 }
36 
37 void DAG::topologicalSort(){
38     stack<int> Stack = stack<int>();
39     bool *visited = new bool[v];
40     for (int i=0;i<v;i++)
41         visited[i] = false;
42 
43     //recursive call tsutil function to store TopoligicalSort
44     //one by one
45     for (int i=0;i<v;i++)
46         if (visited[i] == false)
47             topologicalSortUtil(i,visited,Stack);
48 
49     while(!Stack.empty()){
50         cout<<Stack.top()<<" ";
51         Stack.pop();
52     }
53 }
54 
55 int main(){
56     DAG dag = DAG(9);
57     dag.addEdge(1,6);
58     dag.addEdge(2,3);
59     dag.addEdge(3,6);
60     dag.addEdge(4,0);
61     dag.addEdge(4,1);
62     dag.addEdge(5,2);
63     dag.addEdge(5,0);
64     dag.addEdge(5,1);
65     dag.addEdge(7,8);
66 
67     cout<<"Topological Sort of the given Directed Acyclic Graph(DAG): "<<endl;
68     dag.topologicalSort();
69     cout<<endl;
70 
71     return 0;
72 }