强连通分量的tarjan算法

一、数据集形式

二、数据集

三、实现代码

// Tarjan.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include "time.h"
#include <fstream>
#include<iostream>
#include <stack>
using namespace std;

#define PATH "E://dataset//MapSet//qiangliantongfenliang//test.txt"
class CTreeNode
{
public:
CTreeNode()
{}
~CTreeNode() {}
int value;
CTreeNode *next;
};
class CTree
{
public:
CTree() {}
~CTree() {}
int value;
CTreeNode *next;
CTree *before;
int state;

//tarjan特有变量
int low;
int dfn;
};
CTree* createTree(char* filename, int &length)
{
CTree *tree;
ifstream ReadFile;
int temp;
ReadFile.open(filename, ios::in);//ios::in 表示以只读的方式读取文件
ReadFile >> length;//第一个字符是数组长度
tree = new CTree[length];
//为树赋初值
for (int i = 0; i < length; i++)
{
tree[i].next = NULL;
tree[i].value = i;
tree[i].state = 0;
tree[i].before = NULL;
}
CTreeNode *nt;
while (!ReadFile.eof())            //按空格读取，遇到空白符结束
{
nt = new CTreeNode();       //读出的数据新建一个节点
ReadFile >> temp;
ReadFile>> (nt->value);
nt->next = tree[temp].next;
tree[temp].next = nt;
}
return tree;
}

CTree *tree;
int length;
int t;
stack<int> ss;
int ij;//用来记录数量

void DfsVisit(CTree*tNode)
{
tNode->state = 1;
t++;
tNode->dfn = t;
tNode->low = t;
ss.push(tNode->value);
CTreeNode *p = tNode->next;
while (p != NULL)
{
if (tree[p->value].state == 0)
{
tree[p->value].before = tNode;
DfsVisit(&tree[p->value]);
}
if (tree[p->value].state == 1)
{
//深度优先搜索，向下查找
if (tree[p->value].dfn < tNode->low)
{
tNode->low = tree[p->value].dfn;
}
}
p = p->next;
}
tNode->state = 2;
//回溯父节点
if (tNode->before!=NULL&&(tNode->before->low) > (tNode->low))
{
tNode->before->low=tNode->low;
}
if (tNode->dfn == tNode->low)
{
ij++;
//cout << "第" << ij << "个强连通分量：";
int temp;
do
{
temp = ss.top();
//cout << temp << " ";
ss.pop();
} while (tNode->value!=temp);
//cout << endl;
}

}
void Tarjan()
{
t = 0;
ij = 0;//用于记录强连通分量的数量
for (int i = 0; i < length; i++)
{
if (tree[i].state == 0)
DfsVisit(&tree[i]);
}
}

int main()
{
//读取了文本中的内容，并根据建立其邻接链表
tree = createTree(PATH, length);
//tarjan算法，深度优先搜索得出值
double useTime;
clock_t start, finish;
start = clock();
Tarjan();
cout << "共" << ij << "组强连通分量" << endl;
finish = clock();
useTime = (double)(finish - start) / CLOCKS_PER_SEC * 1000;
printf("%f 毫秒\n", useTime);

system("pause");
return 0;
}