/*
ID: wuqi9395@126.com
PROG:
LANG: C++
*/
#include<map>
#include<set>
#include<queue>
#include<stack>
#include<cmath>
#include<cstdio>
#include<vector>
#include<string>
#include<fstream>
#include<cstring>
#include<ctype.h>
#include<iostream>
#include<algorithm>
using namespace std;
#define INF (1<<30)
#define PI acos(-1.0)
#define mem(a, b) memset(a, b, sizeof(a))
#define rep(i, a, n) for (int i = a; i < n; i++)
#define per(i, a, n) for (int i = n - 1; i >= a; i--)
#define eps 1e-6
#define debug puts("===============")
#define pb push_back
#define mkp make_pair
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define SZ(x) ((int)(x).size())
#define POSIN(x,y) (0 <= (x) && (x) < n && 0 <= (y) && (y) < m)
typedef long long ll;
typedef unsigned long long ULL;
const int maxn = 110;
vector<int> g[maxn];
int n, m, dfn[maxn], low[maxn], scc_cnt, dfs_clock, sccno[maxn];
stack<int> s;
void dfs(int u) {
low[u] = dfn[u] = ++dfs_clock;
s.push(u);
for (int i = 0; i < g[u].size(); i++) {
int v = g[u][i];
if (!dfn[v]) {
dfs(v);
low[u] = min(low[v], low[u]);
} else if (!sccno[v]) low[u] = min(low[u], dfn[v]);
}
if (low[u] == dfn[u]) {
scc_cnt++;
while(1) {
int x = s.top();
s.pop();
sccno[x] = scc_cnt;
if (x == u) break;
}
}
}
void find_scc(int n) {
mem(dfn, 0);
mem(sccno, 0);
scc_cnt = dfs_clock = 0;
for (int i = 1; i <= n; i++) if (!dfn[i]) dfs(i);
}
int in[maxn], out[maxn];
int incnt, outcnt;
int work() {
for (int u = 1; u <= n; u++) {
for (int i = 0; i < g[u].size(); i++) {
int U = sccno[u], V = sccno[g[u][i]];
if (U != V) out[U]++, in[V]++;
}
}
incnt = outcnt = 0;
//cout<<scc_cnt<<endl;
for (int i = 1; i <= scc_cnt; i++) {
if (!in[i]) incnt++;
if (!out[i]) outcnt++;
}
printf("%d\n", incnt);
if (scc_cnt == 1) printf("0\n");
else printf("%d\n", max(incnt, outcnt));
}
int main () {
scanf("%d", &n);
for (int i = 1; i <= n; i++) {
int x;
while(scanf("%d", &x), x) {
g[i].pb(x);
}
}
find_scc(n);
work();
return 0;
}
POJ 1236 Network of Schools(强连通分量)
原文:http://blog.csdn.net/sio__five/article/details/39085799