hdu 3062 2-SAT问题

思路：裸的2-SAT。

#include<map>

#include<set>

#include<cmath>

#include<queue>

#include<cstdio>

#include<vector>

#include<string>

#include<cstdlib>

#include<cstring>

#include<iostream>

#include<algorithm>

#define Maxn 2010

#define Maxm 100010

#define LL __int64

#define Abs(x) ((x)>0?(x):(-x))

#define lson(x) (x<<1)

#define rson(x) (x<<1|1)

#define inf 0x7fffffff

#define Mod 1000000007

using namespace std;

int dfn[Maxn],low[Maxn],id[Maxn],Stack[Maxn],lab,num,e,top,vi[Maxn],n,m;

vector<int> head[Maxn];

void init()

{

    memset(dfn,0,sizeof(dfn));

    memset(low,0,sizeof(low));

    lab=num=top=0;

    memset(vi,0,sizeof(vi));

    memset(id,0,sizeof(id));

    for(int i=0;i<=2*n;i++)

        head[i].clear();

}

void Tarjan(int u)

{

    int i,v,sz;

    dfn[u]=low[u]=++lab;

    Stack[top++]=u;

    vi[u]=1;

    sz=head[u].size();

    for(i=0;i<sz;i++){

        v=head[u][i];

        if(!dfn[v]){

            Tarjan(v);

            low[u]=min(low[v],low[u]);

        }

        if(vi[v])

        low[u]=min(low[u],dfn[v]);

    }

    if(low[u]==dfn[u]){

        ++num;

        do{

          i=Stack[--top];

          id[i]=num;

          vi[i]=0;

        }while(i!=u);

    }

    return ;

}

int main()

{

    int i,j,a,b,c,d;

    while(scanf("%d",&n)!=EOF){

        init();

        scanf("%d",&m);

        for(i=1;i<=m;i++){

            scanf("%d%d%d%d",&a,&b,&c,&d);

            a++;

            b++;

            if(c==0&&d==0)

                head[a].push_back(b+n),head[b].push_back(a+n);

            if(c==0&&d==1)

                head[a].push_back(b),head[b+n].push_back(a+n);

            if(c==1&&d==0)

                head[a+n].push_back(b+n),head[b].push_back(a);

            if(c==1&&d==1)

                head[a+n].push_back(b),head[b+n].push_back(a);

        }

        for(i=1;i<=2*n;i++){

            if(!dfn[i])

                Tarjan(i);

        }

        for(i=1;i<=n;i++)

            if(id[i]==id[i+n])

                break;

        if(i<=n)

            printf("NO\n");

        else

            printf("YES\n");

    }

    return 0;

}