2021-1 计算强连通分量的个数 Kosaraju算法 c++

强连通分量的API

理论准备点这里

实现

#pragma once
#include"Digraph.h"
#include"DepthFirstOrder.h"
class KoarajuSCC
{
    
    
public:
	KoarajuSCC(Digraph& G);

	int count() {
    
     return m_count; }

	bool stronglyConnected(int v, int w) {
    
    
		return (*m_id)[v] == (*m_id)[w];
	}

	int id(int v) {
    
    
		return (*m_id)[v];
	}

private:
	vector<bool>* m_marked = nullptr;
	vector<int>* m_id = nullptr;//几号强连通分量，0-m_count-1
	int m_count = 0;//强连通分量个数

	void dfs(Digraph& G, int v);
};

void testForKoarajuSCC();

#include "KoarajuSCC.h"

KoarajuSCC::KoarajuSCC(Digraph& G)
{
    
    
	m_marked = new vector<bool>(G.V(), false);
	m_id = new vector<int>(G.V(), 0);

	DepthFirstOrder* order = new DepthFirstOrder(G.reverse());
	stack<int>* stk = order->getRePost();
	while (!stk->empty()) {
    
    
		int s = stk->top(); stk->pop();
		if (!m_marked->at(s)) {
    
    
			dfs(G, s);
			m_count++;//完成一次dfs,强联通分量数目加一
		}
	}
}

void KoarajuSCC::dfs(Digraph& G, int v)
{
    
    
	m_marked->at(v) = true;
	m_id->at(v) = m_count;//同一次dfs访问到的都是同一个联通分量
	forIt(G.adj(v)) {
    
    
		int w = *it;
		if (!m_marked->at(w)) {
    
    
			dfs(G, w);
		}
	}
}

void testForKoarajuSCC()
{
    
    
	Digraph G("tinyDG.txt");
	KoarajuSCC scc(G);

	out("strongly connected componentTarjan has ");
	out(scc.count()), hh;
	out("9 belongs to id_"), out(scc.id(9)),hh;
	out("0 belongs to id_"), out(scc.id(0)),hh;
	out("9 0 is strongly connected ? ");
	out(scc.stronglyConnected(0, 9)),hh;
}

测试图

下载文件 tinyDG.txt
头文件见 DepthFirstOrder.h