NOIP2014寻找道路

哭唧唧本想着这么简单的题连调试都没有就交了然后90QAQQQQQQQQQ，良久，突然发现第二次bfs的判重数组居然开在了bfs里面而且没有清0，嘤嘤嘤，加一个清零然后就AC了QAQQQQQQQQQQQ

双bfs不解释没什么好说的

#include<cstdio>
#include<algorithm>
#include<iostream>
#define N 10005
#define M 200005
#define LL long long
using namespace std;
struct wakaka
{
int x,y,next;
}e[M*2];
int u[M],v[M],dis
,vis
,ls
,cnt,q[M*2];
int n,m,S,T;
LL read()
{
LL x=0,f=1;char ch=getchar();
while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
return x*f;
}

void add(int x,int y)
{
int t=++cnt;e[t].x=x;e[t].y=y;e[t].next=ls[x];ls[x]=cnt;
}

void bfs()
{
memset(vis,0,sizeof(vis));
int h=0,t=1;q[t]=T;vis[T]=1;
while (h<t)
{
h++;int x=q[h];
for (int i=ls[x];i!=0;i=e[i].next)
{
if (!vis[e[i].y])
{
q[++t]=e[i].y;
vis[e[i].y]=1;
}
}
}
}

bool check(int x)
{
for (int i=ls[x];i!=0;i=e[i].next)
{
if (!vis[e[i].y]) return 0;
}
return 1;
}

bool work()
{
int h=0,t=1;int vv
;q[t]=S;memset(vv,0,sizeof(vv));vv[S]=1;
while (h<t)
{
h++;int x=q[h];
// cout<<x<<endl;
if (!check(x)) continue;
for (int i=ls[x];i!=0;i=e[i].next)
{
if (e[i].y==T)
{
int ans=dis[h]+1;
printf("%d\n",ans);
return 0;
}
if (!vv[e[i].y])
{
q[++t]=e[i].y;
vv[e[i].y]=1;
dis[t]=dis[h]+1;
}
}
}
return 1;
}

int main()
{
freopen("road.in","r",stdin);
freopen("road.out","w",stdout);
n=read(),m=read();
for (int i=1;i<=m;i++)
{
u[i]=read(),v[i]=read();
if (u[i]!=v[i]) add(v[i],u[i]);
}
S=read();T=read();
bfs();
// for (int i=1;i<=n;i++) cout<<vis[i]<<' ';
// cout<<endl;
if (!vis[S])
{
puts("-1");
return 0;
}
memset(ls,0,sizeof(ls));
cnt=0;
//cout<<-1;
for (int i=1;i<=m;i++)
{
if (u[i]!=v[i]) add(u[i],v[i]);
}
if (work()) puts("-1");
return 0;
}