OJ-Problems-Source/HDOJ/3062_autoAC.cpp
2016-08-30 22:34:56 +08:00

105 lines
2.1 KiB
C++

#include<stdio.h>
#include<string.h>
#include<stack>
using namespace std;
int n,m;
struct edge_node
{
int to;
int next;
};
edge_node edge[5000000];
int head[100000];
int dfn[100000];
int low[100000];
int visit[100000];
int N;
stack<int>sta;
void tarjan_bfs(int cur,int time)
{
visit[cur]=1;
visit[cur^1]=1;
low[cur]=dfn[cur]=time;
sta.push(cur);
for(int i=head[cur];i!=-1;i=edge[i].next)
{
if(visit[edge[i].to]==0)
{
tarjan_bfs(edge[i].to,time++);
time++;
}
if(visit[edge[i].to]==1&&low[cur]>low[edge[i].to])
{
low[cur]=low[edge[i].to];
}
}
if(dfn[cur]==low[cur])
{
N++;
while(!sta.empty()&&sta.top()!=cur)
{
low[sta.top()]=N;
visit[sta.top()]=2;
sta.pop();
}
}
return;
}
void tarjan()
{
N=0;
memset(dfn,0,sizeof(dfn));
memset(low,0,sizeof(low));
memset(visit,0,sizeof(visit));
for(int i=0;i<2*n;i++)
{
if(visit[i]==0)
{
tarjan_bfs(i,1);
}
}
return;
}
int main()
{
while(scanf("%d%d",&n,&m)!=EOF)
{
memset(head,-1,sizeof(head));
int counter=0;
while(m--)
{
int a1,a2,c1,c2;
scanf("%d%d%d%d",&a1,&a2,&c1,&c2);
int temp1;
int temp2;
temp1=2*a1+c1;
temp2=2*a2+c2;
edge[counter].to=temp2;
edge[counter].next=head[temp1^1];
head[temp1^1]=counter++;
edge[counter].to=temp1;
edge[counter].next=head[temp2^1];
head[temp2^1]=counter++;
}
tarjan();
int sign=1;
for(int i=0;i<2*n;i++)
{
if(low[i]==low[i^1])
{
sign=0;
break;
}
}
if(sign==1)
{
printf("YES\n");
}
else
{
printf("NO\n");
}
}
return 0;
}