delete pics to save space

1.2296.cpp

@@ -0,0 +1,87 @@
+#include<cstdio>
+#include<cstring>
+#include<queue>
+#include<algorithm>
+using namespace std;
+const int maxn=10005;
+const int maxm=200005;
+const int oo=0x3f3f3f3f;
+struct Graph
+{
+	struct Edge { int v; Edge *next; };
+	Edge mem[maxm],*G[maxn],*ecnt;
+	Graph() { ecnt=mem; }
+	inline void AddEdge(int u,int v) { ecnt->v=v; ecnt->next=G[u]; G[u]=ecnt++; } 
+};
+Graph G,inv;
+int n,m,x,y,s,t;
+int d[maxn]; bool can[maxn],valid[maxn],vis[maxn];
+void init()
+{
+	valid[t]=true;
+	queue<int> Q;
+	Q.push(t); vis[t]=true;
+	while(Q.size())
+	{
+		int u=Q.front(); Q.pop();
+		for(Graph::Edge *it=inv.G[u];it;it=it->next)
+			if(!vis[it->v])
+			{
+				Q.push(it->v);
+				vis[it->v]=true; valid[it->v]=true;
+			}
+	}
+	for(int i=1;i<=n;i++)
+	{
+		can[i]=(G.G[i]!=0);
+		if(!can[i]) continue;
+		for(Graph::Edge *it=G.G[i];it;it=it->next)
+			if(!valid[it->v])
+			{
+				can[i]=false;
+				break;
+			}
+	}
+	can[t]=true;
+}
+struct Node { int u,dis; };
+inline bool operator<(const Node &a,const Node &b) { return a.dis>b.dis; }
+int dijskra()
+{
+	memset(vis,0,sizeof(vis));
+	memset(d,0x3f,sizeof(d));
+	if(!can[s]) return -1;
+	d[s]=0;
+	priority_queue<Node> Q;
+	Q.push(Node{s,0});
+	while(Q.size())
+	{
+		int u=Q.top().u,dis=Q.top().dis; Q.pop();
+		if(vis[u]) continue;
+		for(Graph::Edge *it=G.G[u];it;it=it->next)
+			if(can[it->v]&&dis+1<d[it->v])
+			{
+				d[it->v]=dis+1;
+				Q.push(Node{it->v,d[it->v]});
+			}
+	}
+	return d[t]<oo?d[t]:-1;
+}
+int main()
+{
+#ifdef local
+	freopen("pro.in","r",stdin);
+#endif
+	scanf("%d%d",&n,&m);
+	while(m-->0)
+	{
+		scanf("%d%d",&x,&y);
+		G.AddEdge(x,y); inv.AddEdge(y,x);
+	}
+	scanf("%d%d",&s,&t);
+	init();
+//	for(int i=1;i<=n;i++) printf("valid[%d]=%d ",i,valid[i]); printf("\n");
+//	for(int i=1;i<=n;i++) printf("can[%d]=%d ",i,can[i]); printf("\n");
+	printf("%d\n",dijskra());
+	return 0;
+}