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strongly connected component.cpp
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strongly connected component.cpp
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#include <stdio.h>
#include <stdlib.h>
#define MaxVertices 15 /* maximum number of vertices */
typedef int Vertex; /* vertices are numbered from 0 to MaxVertices-1 */
typedef struct VNode *PtrToVNode;
struct VNode {
Vertex Vert;
PtrToVNode Next;
};
typedef struct GNode *Graph;
struct GNode {
int NumOfVertices;
int NumOfEdges;
PtrToVNode *Array;
};
PtrToVNode insert(PtrToVNode p, int x)
{
p->Next = (PtrToVNode)malloc(sizeof(struct VNode));
p = p->Next;
p->Vert = x;
p->Next = NULL;
return p;
}
Graph ReadG()
{
int i, j, m, n, x, y;
scanf("%d%d", &m, &n);
Graph p = (Graph)malloc(sizeof(struct GNode));
PtrToVNode *rear = (PtrToVNode*)malloc(m * sizeof(struct VNode));
p->Array = (PtrToVNode*)malloc(m * sizeof(struct VNode));
p->NumOfVertices = m;
p->NumOfEdges = n;
for (i = 0; i<m; i++) {
rear[i] = p->Array[i] = (PtrToVNode)malloc(sizeof(struct VNode));
p->Array[i]->Next = NULL;
}
for (i = 0; i<n; i++) {
scanf("%d%d", &x, &y);
rear[x] = insert(rear[x], y);
}
for (i = 0; i<m; i++) {
PtrToVNode tmp = p->Array[i];
p->Array[i] = p->Array[i]->Next;
tmp->Next = NULL;
free(tmp);
}
return p;
}
void PrintV(Vertex V)
{
printf("%d ", V);
}
void StronglyConnectedComponents(Graph G, void(*visit)(Vertex V));
int main()
{
Graph G = ReadG();
StronglyConnectedComponents(G, PrintV);
return 0;
}
void DFS(Graph G, int* Low, int* Num, int* Stack, int* Instack, int* Visited, int v)
{
static int top = -1;
static int count = 1;
PtrToVNode ptr = G->Array[v];
Stack[++top] = v;
Instack[v] = 1;
Low[v] = Num[v] = count++;
while (ptr != NULL)
{
if (Visited[ptr->Vert])
{
ptr = ptr->Next;
continue;
}
if (Num[ptr->Vert] == 0)
{
int u = ptr->Vert;
DFS(G, Low, Num, Stack, Instack, Visited, u);
if (Low[u] < Low[v])
Low[v] = Low[u];
}
else
{
if (Instack[ptr->Vert])
{
if (Num[ptr->Vert] < Low[v])
{
Low[v] = Num[ptr->Vert];
}
}
}
ptr = ptr->Next;
}
if (Num[v] == Low[v])
{
do {
Instack[Stack[top]] = 0;
Visited[Stack[top]] = 1;
PrintV(Stack[top]);
top--;
} while (Stack[top + 1] != v);
printf("\n");
//printf("%d\n", Stack[top]);
//Visited[Stack[top--]] = 1;
for (int i = 0; i < G->NumOfVertices; i++)
{
if (!Num[i])
DFS(G, Low, Num, Stack, Instack, Visited, i);
}
}
return;
}
void StronglyConnectedComponents(Graph G, void(*visit)(Vertex V))
{
int Low[MaxVertices] = {};
int Num[MaxVertices] = {};
int Instack[MaxVertices] = {};
int Stack[MaxVertices] = {};
int Visited[MaxVertices] = {};
DFS(G, Low, Num, Stack, Instack, Visited, G->NumOfVertices - 1);
system("pause");
}