poj3678 Katu Puzzle（2sat入门好题）

src：poj3678

 

 

AC代码：

#define _CRT_SECURE_NO_WARNINGS
#include<iostream>
#include<stdio.h>
#include<algorithm>
#include<vector>
#include<stack>
using namespace std;
int Max(int a, int b) { return a > b ? a : b; }
int Min(int a, int b) { return a > b ? b : a; }
#define FOR(i,a,b) for(int i=a;i<=b;i++)
typedef long long LL;
typedef unsigned long long ull;
const double INF = 99999999999.0;
const double eps = 1e-6;
#define siz 2200
int n,m;
int dfn[siz],low[siz],id[siz],scc,index;
bool in[siz],flag;
stack<int>st;
vector<int>g[siz];
void init()
{
    scc=index=0;
    flag=true;
    memset(dfn,0,sizeof(dfn));
    memset(low,0,sizeof(low));
    memset(id,0,sizeof(id));
    memset(in,false,sizeof(in));
    while(!st.empty())st.pop();
    for(int i=0;i<2*n;i++)g[i].clear();
}
void add_edge(int u,int v)
{
    g[u].push_back(v);
}
void read()
{
    int a,b,c;
    char s[4];
    for(int i=1;i<=m;i++){
        scanf("%d%d%d%s",&a,&b,&c,s);
        if(strcmp(s,"AND")==0){
            if(c==0){
                add_edge(2*a,2*b+1);add_edge(2*b,2*a+1);
            }
            else if(c==1){
                //add_edge(2*a,2*b);add_edge(2*b,2*a);//可删可留
                add_edge(2*a+1,2*a);add_edge(2*b+1,2*b);
            }
        }
        else if(strcmp(s,"OR")==0){
            if(c==0){
                //add_edge(2*a+1,2*b+1);add_edge(2*b+1,2*a+1);
                add_edge(2*a,2*a+1);add_edge(2*b,2*b+1);
            }
            else if(c==1){
                add_edge(2*a+1,2*b);add_edge(2*b+1,2*a);
            }
        }
        else if(strcmp(s,"XOR")==0){
            if(a==b&&c==0)continue;
            if(c==1){
                add_edge(2*a,2*b+1);add_edge(2*b+1,2*a);
                add_edge(2*b,2*a+1);add_edge(2*a+1,2*b);
            }
            else if(c==0){
                add_edge(2*a,2*b);add_edge(2*b+1,2*a+1);
                add_edge(2*b,2*a);add_edge(2*a+1,2*b+1);
            }
        }
    }
}
void tarjan(int u)
{
    dfn[u]=low[u]=++index;
    st.push(u);in[u]=true;
    for(int i=0;i<g[u].size();i++){
        int v=g[u][i];
        if(dfn[v]==0){
            tarjan(v);
            low[u]=min(low[u],low[v]);
        }
        else if(in[v])low[u]=min(low[u],dfn[v]);
    }
    if(dfn[u]==low[u]){
        int tmp;
        ++scc;
        do{
            tmp=st.top();st.pop();
            id[tmp]=scc;in[tmp]=false;
        }while(tmp!=u);
    }
}
void solve()
{
    for(int i=0;i<2*n;i++)if(dfn[i]==0)tarjan(i);
    for(int i=0;i<n;i++){
        if(id[2*i]==id[2*i+1]){
            printf("NO\n");return;
        }
    }
    printf("YES\n");
}
int main()
{
    while(scanf("%d %d",&n,&m)!=EOF){
        init();
        read();
        solve();
    }
    return 0;
}