// MST_kruskal
void MST_kruskal(MGraph G)
{
int vSet[MAXSIZE]; // 辅助结构，vSet[i] == vSet[j] 表示i,j属于同一个连通分量
for (int vertexNo = 0; vertexNo < G.vertexNum; ++vertexNo)
{
vSet[vertexNo] = vertexNo; // 初始时，所有的顶点均属于不同的连通分量
}
// 处理边
Edge *edge = (Edge*)malloc(G.edgeNum * sizeof(Edge)); // 辅助存储结构，存储所有边
storeEdge(G, edge);
sortEdge(edge, G.edgeNum);
// 找n - 1条边
int edgeNo = 0;
int index = 0;
while (index < G.vertexNum - 1)
{
int s1 = vSet[edge[edgeNo].vex1];
int s2 = vSet[edge[edgeNo].vex2];
if (s1 != s2) // 该边的顶点不属于同一个连通分量
{
mstedge[index] = edge[edgeNo]; // 将该边保存到最小生成树
// 将s2所属的连通分量加入到s1所属的连通分量
for (int vertexNo = 0; vertexNo < G.vertexNum; ++vertexNo)
{
if (s2 == vSet[vertexNo])
{
vSet[vertexNo] = s1;
}
}
index++;
}
edgeNo++;
}
free(edge);
}
void Graph::readGraph()
{
NodeID fromID, toID;
char *contents;
int fd;
struct stat s;
size_t length;
//open
fd = open(inputFileName.c_str(), O_RDONLY);
if (fd == -1)
handle_error("open",ERR_OPENING_FILE);
//obtain file size
if (fstat(fd, &s) == -1)
handle_error("fstat",ERR_READING_FILE);
length = s.st_size;
//map the contents
contents = (char*) mmap(NULL, length, PROT_READ, MAP_PRIVATE, fd, 0);
if (contents == MAP_FAILED)
handle_error("mmap",ERR_MEMORY_ALLOC);
istringstream iss(contents);
iss>>NN>>NE;
cout<<"The number of nodes in the graph is NN = "<<NN <<" and the number of edges is NE = "<<NE<<endl<<endl;
while(iss>>fromID>>toID)
{
storeEdge(fromID,toID);
}
//close input file
munmap(contents,length);
close(fd);
}//end of readGraph()
