delete pics to save space

2.12167.cpp

@@ -0,0 +1,70 @@
+#include<cstdio>
+#include<vector>
+#include<stack>
+#include<cstring>
+#include<algorithm>
+using namespace std;
+const int maxn=20005;
+int T,n,m,in0[maxn],out0[maxn];
+vector<int> G[maxn];
+int dfn[maxn],lowlink[maxn],sccno[maxn],dfs_cnt,scc_cnt;
+stack<int> S;
+void dfs(int u)
+{
+	dfn[u]=lowlink[u]=++dfs_cnt;
+	S.push(u);
+	for(int i=0;i<G[u].size();i++)
+	{
+		int v=G[u][i];
+		if(!dfn[v])
+		{
+			dfs(v);
+			lowlink[u]=min(lowlink[u],lowlink[v]);
+		}
+		else if(!sccno[v]) lowlink[u]=min(lowlink[u],dfn[v]);
+	}
+	if(lowlink[u]==dfn[u])
+	{
+		scc_cnt++;
+		while(true)
+		{
+			int x=S.top(); S.pop();
+			sccno[x]=scc_cnt;
+			if(x==u) break;
+		}
+	}
+}
+int main()
+{
+#ifdef local
+	freopen("pro.in","r",stdin);
+#endif
+	scanf("%d",&T);
+	while(T-->0)
+	{
+		scanf("%d%d",&n,&m);
+		for(int i=1;i<=n;i++) G[i].clear();
+		for(int i=0;i<m;i++)
+		{
+			int u,v; scanf("%d%d",&u,&v);
+			G[u].push_back(v);
+		}
+		dfs_cnt=0; scc_cnt=0;
+		memset(sccno,0,sizeof(sccno));
+		memset(dfn,0,sizeof(dfn));
+		for(int i=1;i<=n;i++) if(!dfn[i]) dfs(i);
+		for(int i=1;i<=scc_cnt;i++) in0[i]=out0[i]=1;
+		for(int u=1;u<=n;u++)
+			for(int i=0;i<G[u].size();i++)
+			{
+				int v=G[u][i];
+				if(sccno[v]!=sccno[u]) in0[sccno[v]]=out0[sccno[u]]=0;
+			}
+		int a=0,b=0;
+		for(int i=1;i<=scc_cnt;i++) a+=in0[i],b+=out0[i];
+		int ans=max(a,b);
+		if(scc_cnt==1) ans=0;
+		printf("%d\n",ans);
+	}
+	return 0;
+}