ZOJ 3232 It's not Floyd Algorithm --强连通分量+Floyd

#include <iostream>
#include <cstdio>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <vector>
#include <stack>
using namespace std;
#define N 207

vector<int> G[N];
int mp[204][204],tG[204][204];
stack<int> stk;
int instk[N],cnt,Time,n;
int low[N],dfn[N],bel[N],num[N];

void tarjan(int u)
{
    low[u] = dfn[u] = ++Time;
    stk.push(u);
    instk[u] = 1;
    for(int i=0;i<G[u].size();i++)
    {
        int v = G[u][i];
        if(!dfn[v])
        {
            tarjan(v);
            low[u] = min(low[u],low[v]);
        }
        else if(instk[v])
            low[u] = min(low[u],dfn[v]);
    }
    if(low[u] == dfn[u])
    {
        cnt++;
        int v;
        do
        {
            v = stk.top();
            stk.pop();
            instk[v] = 0;
            bel[v] = cnt;
            num[cnt]++;
        }while(u != v);
    }
}

void Tarjan()
{
    memset(bel,0,sizeof(bel));
    memset(instk,0,sizeof(instk));
    memset(dfn,0,sizeof(dfn));
    memset(low,0,sizeof(low));
    memset(num,0,sizeof(num));
    Time = cnt = 0;
    while(!stk.empty())
        stk.pop();
    for(int i=1;i<=n;i++)
        if(!dfn[i])
            tarjan(i);
}

void Build()
{
    int i,j;
    memset(tG,0,sizeof(tG));
    for(i=1;i<=n;i++)
    {
        for(j=0;j<G[i].size();j++)
        {
            int v = G[i][j];
            if(bel[i] != bel[v] && mp[i][v])
                tG[bel[i]][bel[v]] = 1;
        }
    }
}

int main()
{
    int i,j,k,u,v;
    while(scanf("%d",&n)!=EOF)
    {
        for(i=0;i<=n;i++)
            G[i].clear();
        for(i=1;i<=n;i++)
        {
            for(j=1;j<=n;j++)
            {
                scanf("%d",&mp[i][j]);
                if(i == j || !mp[i][j])
                    continue;
                G[i].push_back(j);
            }
        }
        Tarjan();
        Build();
        for(k=1;k<=cnt;k++)
        {
            for(i=1;i<=cnt;i++)
            {
                for(j=1;j<=cnt;j++)
                {
                    if(tG[i][j] && tG[i][k] && tG[k][j])
                        tG[i][j] = 0;
                }
            }
        }
        int res = 0;
        for(i=1;i<=n;i++)
            for(j=1;j<=n;j++)
                if(tG[i][j])
                    res++;
        for(i=1;i<=cnt;i++)
        {
            if(num[i] > 1)
                res += num[i];
        }
        printf("%d\n",res);
    }
    return 0;
}