C ++程序检查是否可以在图形中执行拓扑排序
在有向无环图中，我们可以使用拓扑排序以线性顺序对顶点进行排序。
拓扑排序仅适用于有向无环图。在有向无环图(DAG)中，可以有多个拓扑类别。
在下面的C++程序中，我们将执行拓扑排序以检查图中是否存在循环。
演算法
对于功能Topo_Sort
Begin
Define function Topo_Sort()
Declare x to the integer datatype, vstd[] of the Boolean array and Stack as a stack.
Pass them as parameter.
Initialize vstd[x] = true to mark the current node as vstd.
Declare an iterator i.
for (i = a[x].begin(); i != a[x].end(); ++i)
if (!vstd[*i]) then
Call Topo_Sort(*i, vstd, Stack) function.
Call push() function to insert values into stack.
End.示例
#include<iostream>
#include <list>
#include <stack>
using namespace std;
class grph { // Class to represent a graph
int ver;
list<int> *a; // Pointer to an array containing adjacency listsList
void Topo_Sort(int x, bool vstd[], stack<int> &Stack); // A function used by TopologicalSort
public:
grph(int ver); // Constructor of grpf
void Insert_Edge(int x, int y); // to insert an edge to graph
void Topol_Sort(); // prints a Topological Sort of the complete graph
};
grph::grph(int ver) {
this->ver = ver;
a = new list<int>[ver];
}
void grph::Insert_Edge(int x, int y) {
a[x].push_back(y); // Add y to x’s list.
}
//使用的递归函数
void grph::Topo_Sort(int x, bool vstd[], stack<int> &Stack) {
vstd[x] = true; // Mark the current node as vstd.
list<int>::iterator i;
for (i = a[x].begin(); i != a[x].end(); ++i)
if (!vstd[*i])
Topo_Sort(*i, vstd, Stack);
//将当前顶点推入堆栈以存储结果
Stack.push(x);
}
void grph::Topol_Sort() {
stack<int> Stack;
//将所有顶点标记为非vstd-
bool *vstd = new bool[ver];
for (int i = 0; i < ver; i++)
vstd[i] = false;
for (int i = 0; i < ver; i++)
if (vstd[i] == false)
Topo_Sort(i, vstd, Stack);
while (Stack.empty() == false) {
cout << Stack.top() << " ";
Stack.pop();
}
}
int main() {
grph g(6); // Create a graph given in the above diagram
g.Insert_Edge(5, 2);
g.Insert_Edge(5, 0);
g.Insert_Edge(4, 0);
g.Insert_Edge(4, 1);
g.Insert_Edge(2, 3);
g.Insert_Edge(3, 1);
cout << "Topological Sort of the graph is: \n";
g.Topol_Sort();
return 0;
}输出结果
Topological Sort of the graph is: 5 4 2 3 1 0