UVALive 5010 Go Deeper 2sat

二分答案，2sat判定。

//#pragma comment(linker, "/STACK:1024000000,1024000000")

#include<cstdio>

#include<cstring>

#include<cstdlib>

#include<algorithm>

#include<iostream>

#include<sstream>

#include<cmath>

#include<climits>

#include<string>

#include<map>

#include<queue>

#include<vector>

#include<stack>

#include<set>

using namespace std;

typedef long long ll;

typedef unsigned long long ull;

typedef pair<int,int> pii;

#define pb(a) push(a)

#define INF 0x1f1f1f1f

#define lson idx<<1,l,mid

#define rson idx<<1|1,mid+1,r

#define PI  3.1415926535898

template<class T> T min(const T& a,const T& b,const T& c) {

    return min(min(a,b),min(a,c));

}

template<class T> T max(const T& a,const T& b,const T& c) {

    return max(max(a,b),max(a,c));

}

void debug() {

#ifdef ONLINE_JUDGE

#else

freopen("in.txt","r",stdin);

    //freopen("d:\\out1.txt","w",stdout);

#endif

}

int getch() {

    int ch;

    while((ch=getchar())!=EOF) {

        if(ch!=‘ ‘&&ch!=‘\n‘)return ch;

    }

    return EOF;

}
const int maxn=205;

struct TwoSat

{

    int n;

    vector<int> g[maxn*2];

    bool mark[maxn*2];

    int s[maxn*2],c;

    bool dfs(int x)

    {

        if(mark[x^1])return false;

        if(mark[x])return true;

        mark[x]=true;

        s[c++]=x;

        for(int i=0;i<g[x].size();i++)

        {

            if(!dfs(g[x][i]))return false;

        }

        return true;

    }

    void init(int n)

    {

        this->n=n;

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

            g[i].clear();

        memset(mark,0,sizeof(mark));

    }

    void add_clause(int x,int xval,int y,int yval)

    {

        x=x*2+xval;

        y=y*2+yval;

        g[x].push_back(y^1);

        g[y].push_back(x^1);

    }

    bool solve()

    {

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

        {

            if(!mark[i]&&!mark[i+1])

            {

                c=0;

                if(!dfs(i))

                {

                    while(c>0)mark[s[--c]]=0;

                    if(!dfs(i+1))return false;

                }

            }

        }

        return true;

    }

};
TwoSat solver;
const int maxm=10005;

int a[maxm],b[maxm],c[maxm];

int n,m;

int check(int k)

{

    solver.init(n);

    for(int i=0;i<k;i++)

    {

        if(c[i]==0)

        {

            int x=a[i],y=b[i];

            solver.add_clause(x,0,y,0);

        }

        if(c[i]==2)

        {

            int x=a[i],y=b[i];

            solver.add_clause(x,1,y,1);

        }

        if(c[i]==1)

        {

            int x=a[i],y=b[i];

            solver.add_clause(x,0,y,1);

            solver.add_clause(x,1,y,0);

        }

    }

    return solver.solve();

}

int main()

{

    int t;

    scanf("%d",&t);

    for(int ca=1;ca<=t;ca++)

    {

        scanf("%d%d",&n,&m);

        for(int i=0;i<m;i++)

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

        int l=0,r=m+1;

        while(l<r)

        {

            int mid=(r+l)>>1;

            if(check(mid))

                l=mid+1;

            else r=mid;

        }

        printf("%d\n",l-1);

    }

    return 0;

}

UVALive 5010 Go Deeper 2sat