正文
HDU-4665 Unshuffle 搜索 | 2-SAT
小程序：扫一扫查出行【扫一扫了解最新限行尾号】
复制小程序
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 ;
}
