POJ-2296 Map Labeler 2sat

　　题目链接：http://poj.org/problem?id=2296

　　二分+2sat，每个点的上下两个方向为2sat的两个状态。

 //STATUS:C++_AC_16MS_536KB
 #include <functional>
 #include <algorithm>
 #include <iostream>
 //#include <ext/rope>
 #include <fstream>
 #include <sstream>
 #include <iomanip>
 #include <numeric>
 #include <cstring>
 #include <cassert>
 #include <cstdio>
 #include <string>
 #include <vector>
 #include <bitset>
 #include <queue>
 #include <stack>
 #include <cmath>
 #include <ctime>
 #include <list>
 #include <set>
 #include <map>
 using namespace std;
 //using namespace __gnu_cxx;
 //define
 #define pii pair<int,int>
 #define mem(a,b) memset(a,b,sizeof(a))
 #define lson l,mid,rt<<1
 #define rson mid+1,r,rt<<1|1
 #define PI acos(-1.0)
 //typedef
 typedef long long LL;
 typedef unsigned long long ULL;
 //const
 const int N=;
 const int INF=0x3f3f3f3f;
 const int MOD=,STA=;
 const LL LNF=1LL<<;
 const double EPS=1e-;
 const double OO=1e15;
 const int dx[]={-,,,};
 const int dy[]={,,,-};
 const int day[]={,,,,,,,,,,,,};
 //Daily Use ...
 inline int sign(double x){return (x>EPS)-(x<-EPS);}
 template<class T> T gcd(T a,T b){return b?gcd(b,a%b):a;}
 template<class T> T lcm(T a,T b){return a/gcd(a,b)*b;}
 template<class T> inline T lcm(T a,T b,T d){return a/d*b;}
 template<class T> inline T Min(T a,T b){return a<b?a:b;}
 template<class T> inline T Max(T a,T b){return a>b?a:b;}
 template<class T> inline T Min(T a,T b,T c){return min(min(a, b),c);}
 template<class T> inline T Max(T a,T b,T c){return max(max(a, b),c);}
 template<class T> inline T Min(T a,T b,T c,T d){return min(min(a, b),min(c,d));}
 template<class T> inline T Max(T a,T b,T c,T d){return max(max(a, b),max(c,d));}
 //End

 int nod[N][];
 int first[N*],next[N*N*],vis[N*],S[N*];
 int T,n,mt,cnt;

 struct Edge{
     int u,v;
 }e[N*N*];

 void adde(int a,int b)
 {
     e[mt].u=a,e[mt].v=b;
     next[mt]=first[a];first[a]=mt++;
 }

 int dfs(int u)
 {
     if(vis[u^])return ;
     if(vis[u])return ;
     int i;
     vis[u]=;
     S[cnt++]=u;
     for(i=first[u];i!=-;i=next[i]){
         if(!dfs(e[i].v))return ;
     }
     return ;
 }

 int Twosat()
 {
     int i,j;
     for(i=;i<n;i+=){
         if(vis[i] || vis[i^])continue;
         cnt=;
         if(!dfs(i)){
             while(cnt)vis[S[--cnt]]=;
             if(!dfs(i^))return ;
         }
     }
     return ;
 }

 int judge(double *a1,double *a2,double *b1,double *b2)
 {
     if(Max(a1[],a2[])<=Min(b1[],b2[])
        || Min(a1[],a2[])>=Max(b1[],b2[])
        || Max(a1[],a2[])<=Min(b1[],b2[])
        || Min(a1[],a2[])>=Max(b1[],b2[]))return ;
     return ;
 }

 void init(double limt)
 {
     int i,j,x,y;
     double a1[],a2[],b1[],b2[];
     mt=;mem(vis,);
     mem(first,-);
     for(i=;i<n;i++){
         for(j=i+;j<n;j++){
             x=i<<;y=j<<;
             a1[]=nod[i][]-limt/,a1[]=nod[i][];b1[]=nod[j][]-limt/,b1[]=nod[j][];
             a2[]=nod[i][]+limt/,b2[]=nod[j][]+limt/;
             a2[]=nod[i][]-limt;b2[]=nod[j][]-limt;
             if(judge(a1,a2,b1,b2)){
                 adde(x,y^);adde(y,x^);
             }
             b2[]=nod[j][]+limt;
             if(judge(a1,a2,b1,b2)){
                 adde(x,y);adde(y^,x^);
             }
             a2[]=nod[i][]+limt;b2[]=nod[j][]-limt;
             if(judge(a1,a2,b1,b2)){
                 adde(x^,y^);adde(y,x);
             }
             b2[]=nod[j][]+limt;
             if(judge(a1,a2,b1,b2)){
                 adde(x^,y);adde(y^,x);
             }
         }
     }
 }

 int binary(int l,int r)
 {
     int mid;
     while(l<r){
         mid=(l+r)>>;
      //   printf("%d %d\n",l,r);
         init(mid);
         if(Twosat())l=mid+;
         else r=mid;
     }
     return l;
 }

 int main()
 {
  //   freopen("in.txt","r",stdin);
     int i,j;
     scanf("%d",&T);
     while(T--)
     {
         scanf("%d",&n);
         for(i=;i<n;i++){
             scanf("%d%d",&nod[i][],&nod[i][]);
         }

         printf("%d\n",binary(,)-);
     }
     return ;
 }