本文实现了有向图，无向图的邻接矩阵表示，并且实现了从创建到销毁图的各种操作。
以及两种图的深度优先遍历，广度优先遍历，Dijkstra最短路径算法，Prim最小生成树算法，有向图的拓扑排序算法。
通过一个全局变量控制当前图为有向图还是无向图。
若为无向图，则生成的邻接矩阵是对称的，有向图则不对称。
可结合我的另一篇文章（图的邻接表表示）看。
PS: 等有时间了作详细的讲解。
#include <iostream>
#include <climits>
#include <sstream>
#include <queue>
using namespace std;
const bool UNDIGRAPH = 0;
struct Graph
{
string *vertexLabel;//the number of the labels is equal to vertexes
int vertexes;
int edges;
int **AdjMat;
bool *visited;//only for DFS,BFS,Dijkstra
int *distance; //only for Dijkstra
int *path;//only for Dijkstra
};
void BuildGraph(Graph *&graph, int n)
{
if (graph == NULL)
{
graph = new Graph;
graph->vertexes = n;
graph->edges = 0;
graph->AdjMat = new int *[n];
graph->vertexLabel = new string[n];
graph->visited = new bool[n];
graph->distance = new int[n];
graph->path = new int[n];
for (int i = 0; i < graph->vertexes; i++)
{
stringstream ss;
ss<<"v" << i+1;
ss >> graph->vertexLabel[i];
graph->visited[i] = false;
graph->distance[i] = INT_MAX;
graph->path[i] = -1;
graph->AdjMat[i] = new int[n];
if(UNDIGRAPH)
memset(graph->AdjMat[i],0, n * sizeof(int));
else
for (int j = 0; j < graph->vertexes; j++)
{
if(i == j)
graph->AdjMat[i][j] = 0;
else
graph->AdjMat[i][j] = INT_MAX;
}
}
}
}
void MakeEmpty(Graph *&graph)
{
if(graph == NULL)
return;
delete []graph->vertexLabel;
delete []graph->visited;
delete []graph->distance;
delete []graph->path;
for (int i = 0; i < graph->vertexes; i++)
{
delete []graph->AdjMat[i];
}
delete []graph->AdjMat;
delete graph;
}
void AddEdge(Graph *graph,int v1, int v2, int weight)
{
if (graph == NULL) return;
if (v1 < 0 || v1 > graph->vertexes-1) return;
if (v2 < 0 || v2 > graph->vertexes-1) return;
if (v1 == v2) return; //no loop is allowed
if(UNDIGRAPH)
{
if (graph->AdjMat[v1][v2] == 0)//not exist,edges plus 1
graph->edges++;
graph->AdjMat[v1][v2] = graph->AdjMat[v2][v1] = weight;
}
else
{
if (graph->AdjMat[v1][v2] == 0 || graph->AdjMat[v1][v2] == INT_MAX)//not exist,edges plus 1
graph->edges++;
graph->AdjMat[v1][v2] = weight;
}
}
void RemoveEdge(Graph *graph, int v1, int v2)
{
if (graph == NULL) return;
if (v1 < 0 || v1 > graph->vertexes-1) return;
if (v2 < 0 || v2 > graph->vertexes-1) return;
if (v1 == v2) return; //no loop is allowed
if (UNDIGRAPH)
{
if (graph->AdjMat[v1][v2] == 0)//not exists,return
return;
graph->AdjMat[v1][v2] = graph->AdjMat[v2][v1] = 0;
graph->edges--;
}
else
{
if (graph->AdjMat[v1][v2] == 0 || graph->AdjMat[v1][v2] == INT_MAX)//not exists,return
return;
graph->AdjMat[v1][v2] = INT_MAX;
graph->edges--;
}
}
int GetIndegree(Graph *graph, int v)
{
if(graph == NULL) return -1;
if(v < 0 || v > graph->vertexes -1) return -2;
if(UNDIGRAPH) return -3;
int degree = 0;
for (int i = 0; i < graph->vertexes; i++)
{
if(graph->AdjMat[i][v] != 0 && graph->AdjMat[i][v] != INT_MAX)
degree++;
}
return degree;
}
int GetOutdegree(Graph *graph, int v)
{
if(graph == NULL) return -1;
if(v < 0 || v > graph->vertexes -1) return -2;
if(UNDIGRAPH) return -3;
int degree = 0;
for (int i = 0; i < graph->vertexes; i++)
{
if(graph->AdjMat[v][i] != 0 && graph->AdjMat[v][i] != INT_MAX)
degree++;
}
return degree;
}
int GetDegree(Graph *graph, int v)
{
if(graph == NULL) return -1;
if(v < 0 || v > graph->vertexes -1) return -2;
if(UNDIGRAPH)
{
int degree = 0;
for (int i = 0; i < graph->vertexes; i++)
{
if(graph->AdjMat[v][i] != 0)
degree++;
}
return degree;
}
else
return GetIndegree(graph,v) + GetOutdegree(graph,v);
}
void PrintGraph(Graph *graph)
{
if(graph == NULL)
return;
cout << "Vertex: " << graph->vertexes <<"\n";
cout << "Edge: " << graph->edges << "\n";
for (int i = 0; i < graph->vertexes; i++)
{
cout << " "<< graph->vertexLabel[i];
}
cout << "\n";
for (int i = 0; i < graph->vertexes; i++)
{
for (int j = 0; j < graph->vertexes; j++)
{
if(j == 0)
cout << graph->vertexLabel[i] << " ";
if(graph->AdjMat[i][j] == INT_MAX)
cout << "~" << " ";
else
cout << graph->AdjMat[i][j] << " ";
}
cout << "\n";
}
cout << "\n";
}
//depth first search (use stack or recursion)
//DFS is similar to preorder traversal of trees
void DFS(Graph *graph, int i)
{
if (!graph->visited[i])
{
cout << graph->vertexLabel[i] << " ";
graph->visited[i] = true;
}
for (int j = 0; j < graph->vertexes; j++)
{
if (UNDIGRAPH)
{
if (graph->AdjMat[i][j] != 0 && !graph->visited[j])
DFS(graph,j);
}
else
{
if (graph->AdjMat[i][j] != INT_MAX && !graph->visited[j])
DFS(graph,j);
}
}
}
void BeginDFS(Graph *graph)
{
if(graph == NULL) return;
cout << "DFS\n";
for (int i = 0; i < graph->vertexes; i++)
graph->visited[i] = false;
for (int i = 0; i < graph->vertexes; i++)
DFS(graph,i);
}
//breadth first search(use queue)
//BFS is similar to leverorder traversal of trees
//all of the vertexes will be searched once no matter how the digraph is constructed
void BFS(Graph *graph)
{
if(graph == NULL)
return;
cout << "BFS\n";
memset(graph->visited,false,graph->vertexes * sizeof(bool));
queue<int> QVertex;
for (int i = 0; i < graph->vertexes; i++)
{
if (!graph->visited[i])
{
QVertex.push(i);
cout << graph->vertexLabel[i] << " ";
graph->visited[i] = true;
while(!QVertex.empty())
{
int vtxNO = QVertex.front();
QVertex.pop();
for (int j = 0; j < graph->vertexes; j++)
{
if (UNDIGRAPH)
{
if(!graph->visited[j] && graph->AdjMat[vtxNO][j]!=0)
{
cout << graph->vertexLabel[j] << " ";
graph->visited[j] = true;
QVertex.push(j);
}
}
else
{
if(!graph->visited[j] && graph->AdjMat[vtxNO][j]!=INT_MAX)
{
cout << graph->vertexLabel[j] << " ";
graph->visited[j] = true;
QVertex.push(j);
}
}
}
}
}
}
cout << "\n";
}
//after executing this function,the value of AdjMat changed
void TopologicalSort(Graph *graph)
{
if(UNDIGRAPH) return;
if(graph == NULL) return;
cout << "TopologicalSort"<<"\n";
int counter = 0;
queue <int> qVertex;
for (int i = 0; i < graph->vertexes; i++)
{
if(GetIndegree(graph,i) == 0)
qVertex.push(i);
}
while (!qVertex.empty())
{
int vertexNO = qVertex.front();
counter++;
cout << graph->vertexLabel[vertexNO];
if(counter != graph->vertexes)
cout << " > ";
qVertex.pop();
for (int i = 0; i < graph->vertexes; i++)
{
if(i == vertexNO)
continue;
if (GetIndegree(graph,i) != 0)
{
graph->AdjMat[vertexNO][i] = INT_MAX;//indegree--
if(GetIndegree(graph,i) == 0)
qVertex.push(i);
}
}
}
cout << "\n";
}
void Dijkstra(Graph *graph, int v)
{
if(graph == NULL) return;
if(v < 0 || v > graph->vertexes-1) return;
for (int i = 0; i < graph->vertexes; i++)
{
graph->visited[i] = false;
graph->distance[i] = INT_MAX;//can delete this line,as initialized in BuildGraph
graph->path[i] = -1;
}
graph->distance[v] = 0;//the rest are all INT_MAX
while(1)
{
int minDisInx = -1;
int minDis = INT_MAX;
for (int i = 0; i < graph->vertexes; i++)
{
if(!graph->visited[i])
{
if(graph->distance[i] < minDis)
{
minDis = graph->distance[i];
minDisInx = i;
}
}
}
if(minDisInx == -1)//all visited
break;
graph->visited[minDisInx] = true;
for (int i = 0; i < graph->vertexes; i++)
{
//unvisited and adjacent to current vertex
//&& graph->AdjMat[minDisInx][i]!=0 is for undigraph
if (!graph->visited[i] && graph->AdjMat[minDisInx][i]!=INT_MAX && graph->AdjMat[minDisInx][i]!=0)
{
if (graph->distance[minDisInx] + graph->AdjMat[minDisInx][i] < graph->distance[i])
{
graph->distance[i] = graph->distance[minDisInx] + graph->AdjMat[minDisInx][i];
graph->path[i] = minDisInx;
cout << graph->vertexLabel[i] << " Updated to " << graph->distance[i] <<"\n";
}
}
}
}
cout << "Vertex Visited Distance Path\n";
for (int i = 0; i < graph->vertexes; i++)
{
cout << graph->vertexLabel[i]<< " ";
cout << graph->visited[i]<< " ";
cout << graph->distance[i]<< " ";
if(graph->path[i] == -1)
cout << "NONE\n";
else
cout << graph->vertexLabel[graph->path[i]]<< "\n";
}
}
//almost for undigraph
void Prim(Graph *graph, int v)
{
if(graph == NULL) return;
if(v < 0 || v > graph->vertexes-1) return;
for (int i = 0; i < graph->vertexes; i++)
{
graph->visited[i] = false;
graph->distance[i] = INT_MAX;//can delete this line,as initialized in BuildGraph
graph->path[i] = -1;
}
graph->distance[v] = 0;//the rest are all INT_MAX
while(1)
{
int minDisInx = -1;
int minDis = INT_MAX;
for (int i = 0; i < graph->vertexes; i++)
{
if(!graph->visited[i])
{
if(graph->distance[i] < minDis)
{
minDis = graph->distance[i];
minDisInx = i;
}
}
}
if(minDisInx == -1)//all visited
break;
graph->visited[minDisInx] = true;
for (int i = 0; i < graph->vertexes; i++)
{
//unvisited and adjacent to current vertex
//&& graph->AdjMat[minDisInx][i]!=0 is for undigraph
if (!graph->visited[i] && graph->AdjMat[minDisInx][i]!=INT_MAX && graph->AdjMat[minDisInx][i]!=0)
{
if (graph->AdjMat[minDisInx][i] < graph->distance[i])
{
graph->distance[i] = graph->AdjMat[minDisInx][i];
graph->path[i] = minDisInx;
cout << graph->vertexLabel[i] << " Updated to " << graph->distance[i] <<"\n";
}
}
}
}
cout << "Vertex Visited Distance Path\n";
for (int i = 0; i < graph->vertexes; i++)
{
cout << graph->vertexLabel[i]<< " ";
cout << graph->visited[i]<< " ";
cout << graph->distance[i]<< " ";
if(graph->path[i] == -1)
cout << "NONE\n";
else
cout << graph->vertexLabel[graph->path[i]]<< "\n";
}
}
int main()
{
Graph *graph = NULL;
BuildGraph(graph,7);
PrintGraph(graph);
//for simple test, 0 indexed
/*AddEdge(graph,0,1,1);
AddEdge(graph,0,2,1);
AddEdge(graph,1,3,1);*/
//for TopologicalSort
//0 indexed
/*AddEdge(graph,0,1,1);
AddEdge(graph,0,2,1);
AddEdge(graph,0,3,1);
AddEdge(graph,1,3,1);
AddEdge(graph,1,4,1);
AddEdge(graph,2,5,1);
AddEdge(graph,3,2,1);
AddEdge(graph,3,5,1);
AddEdge(graph,3,6,1);
AddEdge(graph,4,3,1);
AddEdge(graph,4,6,1);
AddEdge(graph,6,5,1);*/
//for Dijkstra(shortest path),Prim(minimum spanning tree)
//0 indexed
AddEdge(graph,0,1,2);
AddEdge(graph,0,3,1);
AddEdge(graph,1,3,3);
AddEdge(graph,1,4,10);
AddEdge(graph,2,0,4);
AddEdge(graph,2,5,5);
AddEdge(graph,3,2,2);
AddEdge(graph,3,4,2);
AddEdge(graph,3,5,8);
AddEdge(graph,3,6,4);
AddEdge(graph,4,6,6);
AddEdge(graph,6,5,1);
PrintGraph(graph);
BeginDFS(graph);
cout << "\n";
BFS(graph);
for (int i = 0; i < graph->vertexes; i++)
{
cout << "\n";
Dijkstra(graph,i);
}
Prim(graph,0);
TopologicalSort(graph);
MakeEmpty(graph);
return 0;
}