|poj 1236|强连通分量|Network of Schools

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poj 1236
tarjan
#include<cstdio>#include<cstring>#include<algorithm>#include<vector>#include<stack>#define ms(i, j) memset(i, j, sizeof i)#define FN2 "poj1236" using namespace std;const int MAXN = 100 + 5;vector<int> G[MAXN];stack<int> s;int n, low[MAXN], dn[MAXN], tb, ex[MAXN];int cnt, scc_out[MAXN], scc_in[MAXN], scc_belong[MAXN];void tarjan(int u){    low[u] = dn[u] = ++tb;    s.push(u), ex[u] = -1;    for (int i=0;i<G[u].size();i++)    {        int v = G[u][i];        if (ex[v]==0)        {            tarjan(v);            low[u] = min(low[u], low[v]);        } else if (ex[v]==-1)        {            low[u] = min(low[u], dn[v]);        }    }    if (low[u]==dn[u])    {        int e;        cnt++;        do        {            e = s.top(); s.pop();            scc_belong[e] = cnt;            ex[e] = 1;        } while (u!=e);    }}void rebuild(){    for (int u=1;u<=n;u++)    {        for (int i=0;i<G[u].size();i++)        {            int v = G[u][i];            if (scc_belong[u]!=scc_belong[v])            {                scc_out[scc_belong[u]] = 1;                scc_in[scc_belong[v]] = 1;            }        }    }}void init(){    for (int i=1;i<=n;i++)    {        low[i] = dn[i] = ex[i] = scc_out[i] = scc_in[i] = scc_belong[i] = 0;        G[i].clear();    }    tb = cnt = 0;    for (int i=1;i<=n;i++)    {        int x;        while (scanf("%d", &x)==1&&x)        {            G[i].push_back(x);        }    }}void solve(){    for (int i=1;i<=n;i++)    if (!dn[i]) tarjan(i);    rebuild();    int ans = 0, ansin = 0, ansout = 0;    for (int i=1;i<=cnt;i++) if (!scc_in[i]) ansin++;    for (int i=1;i<=cnt;i++) if (!scc_out[i]) ansout++;    ans = max(ansin, ansout);    if (cnt==1) printf("1\n0\n"); else printf("%d\n%d\n", ansin, ans);}int main(){    #ifndef ONLINE_JUDGE    freopen(FN2".in","r",stdin);    freopen(FN2".out","w",stdout);    #endif    while (scanf("%d", &n)==1)    {        init();        solve();    }    return 0;}
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