HDU-4665 Unshuffle 搜索 | 2-SAT

　　题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=4665

　　本题的2-SAT建图颇为复杂，有时间再来填坑（自己写的一直挂着，标程建图太复杂了）。。。然后用暴力搜索，用一个栈保存第一个序列就可以了，因为题目是SPG，并且重复的最多只有四个，所以搜索很好过。。

 //STATUS:C++_AC_62MS_276KB
 #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;
 //#pragma comment(linker,"/STACK:102400000,102400000")
 //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 __int64 LL;
 typedef unsigned __int64 ULL;
 //const
 const int N=;
 const int INF=0x3f3f3f3f;
 const int MOD= ,STA=;
 const LL LNF=1LL<<;
 const double EPS=1e-;
 const double OO=1e30;
 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 num[N],sta[N],vis[N];
 int T,n,top1,top2,mid;

 bool dfs(int u)
 {
     if(top2==mid)return true;
     if(top1<mid){
         vis[u]=;
         sta[top1++]=num[u];
         if(dfs(u+))return true;
         top1--;
     }
     if(num[u]==sta[top2]){
         vis[u]=;
         top2++;
         if(dfs(u+))return true;
         vis[u]=;
         top2--;
     }
     return false;
 }

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

         top1=top2=;
         dfs();

         for(i=;i<n;i++)
             printf("%d",vis[i]);
         putchar('\n');
     }
     return ;
 }

2-SAT(WA):

 /*   WA   */
 #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;
 //#pragma comment(linker,"/STACK:102400000,102400000")
 //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 __int64 LL;
 typedef unsigned __int64 ULL;
 //const
 const int N=;
 const int INF=0x3f3f3f3f;
 const int MOD= ,STA=;
 const LL LNF=1LL<<;
 const double EPS=1e-;
 const double OO=1e30;
 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

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

 int first[N<<],next[N<<],vis[N<<],S[N<<];
 int num[N];
 int T,n,mt,cnt;

 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 cnt2[N],tot[N],w[N][];
 void Init()
 {
     int i,j,t;
     mt=;mem(vis,);
     mem(first,-);
     mem(tot,);
     for(i=;i<n;i++)w[num[i]][tot[num[i]]++]=i;
     mem(cnt2,);
     for(i=;i<n;i++){
         t=num[i];
         cnt2[t]++;
         if(cnt2[t]==){
             adde((i<<)^,i<<);
             adde(i<<,(w[t][tot[t]-]<<)^);
             adde(w[t][tot[t]-]<<,(i<<)^);
             if(tot[t]==){
                 for(j=w[t][]+;j<n;j++){
                     if(w[num[j]][]==j && w[num[j]][]<j && w[num[j]][]>i){
                         adde(i<<,(w[t][]<<)^);
                         break;
                     }
                 }
             }
         }
         else if(cnt2[t]==){
             adde(w[t][]<<,(w[t][]<<)^);
             adde((w[t][]<<)^,w[t][]<<);
             adde(w[t][]<<,(w[t][]<<)^);
             adde((w[t][]<<)^,w[t][]<<);
         }
     }
 }

 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",&num[i]);

         Init();
         n<<=;
         int t=Twosat();
     //    printf("%d\n",t);

         for(i=;i<n;i+=)
             printf("%d",vis[i]);
         putchar('\n');
     }
     return ;
 }