[Tarjan缩点 拓扑序DP] SRM 499 1000pts

<span style="font-family:Microsoft YaHei;font-size:18px;color:#000066;">#include<cstdio>
#include<cstdlib>
#include<algorithm>
#include<cstring>
#include<bitset>
#define cl(x) memset(x,0,sizeof(x))
using namespace std;
typedef long long ll;

inline char nc()
{
static char buf[100000],*p1=buf,*p2=buf;
if (p1==p2) { p2=(p1=buf)+fread(buf,1,100000,stdin); if (p1==p2) return EOF; }
return *p1++;
}

inline void read(int &x)
{
char c=nc(),b=1;
for (;!(c>='0' && c<='9');c=nc()) if (c=='-') b=-1;
for (x=0;c>='0' && c<='9';x=x*10+c-'0',c=nc()); x*=b;
}

inline int read(char *s){
int len=0; char c=nc();
for (;!(c>='A' && c<='D');c=nc());
for (;c>='A' && c<='D';s[++len]=c,c=nc()); s[++len]=0; return len-1;
}

const int L=35;
const int N=6005;

long double fac[L];

inline void Pre(){
fac[0]=1;
for (int i=1;i<L;i++) fac[i]=fac[i-1]*i;
}

struct abcd{
int a,b,c,d;
abcd(int a=0,int b=0,int c=0,int d=0):a(a),b(b),c(c),d(d) { }
}S
;

int n,m;
int icnt,back[L][L][L][L];
ll val
;

struct Stack{
int s
,p;
void clear(){ p=0; cl(s); }
void push(int x){ s[++p]=x; }
void pop(){ s[p--]=0; }
int top(){ return s[p]; }
bool empty(){ return p==0; }
}Sta;

struct edge{
int u,v; int next;
}G[N<<10];
int head
,inum;

bitset<N> jud
;

inline void add(int u,int v,int p)
{
G[p].u=u; G[p].v=v; G[p].next=head[u]; head[u]=p;
}

int cnt; ll tot
;
int clk,pre
,low
,scc
;

#define V G[p].v
inline void Tarjan(int u)
{
low[u]=pre[u]=++clk;
Sta.push(u);
for (int p=head[u];p;p=G[p].next)
if (!pre[V])
Tarjan(V),low[u]=min(low[u],low[V]);
else if (!scc[V])
low[u]=min(low[u],pre[V]);
if (low[u]==pre[u])
{
++cnt;
while (!Sta.empty())
{
int x=Sta.top(); Sta.pop();
scc[x]=cnt; tot[cnt]+=val[x];
if (x==u) break;
}
}
}

int pnt,lst
;

inline void dfs(int u){
pre[u]=1;
for (int p=head[u];p;p=G[p].next) if (!pre[V]) dfs(V);
lst[++pnt]=u;
}

ll f
;

inline void Solve()
{
memset(pre,0,sizeof(pre));
for (int i=1;i<=cnt;i++)
if (!pre[i])
dfs(i);
reverse(lst+1,lst+pnt+1);
for (int i=1;i<=cnt;i++)
f[i]=tot[i];
for (int i=1;i<=pnt;i++)
{
int u=lst[i];
for (int p=head[u];p;p=G[p].next)
f[V]=max(f[V],f[u]+tot[V]);
}
ll ans=0;
for (int i=1;i<=cnt;i++)
ans=max(ans,f[i]);
printf("%lld\n",ans);
}

int main()
{
char s[L],t[L]; int len;
int a,b,c,d;
int a2,b2,c2,d2,a1,b1,c1,d1;
freopen("return.in","r",stdin);
freopen("return.out","w",stdout);
Pre();
read(n); read(m);
for (a=0;a<=n;a++)
for (b=0;a+b<=n;b++)
for (c=0;a+b+c<=n;c++)
{
d=n-a-b-c;
S[++icnt]=abcd(a,b,c,d);
val[icnt]=(ll)(fac
/fac[a]/fac[b]/fac[c]/fac[d]+0.5);
back[a][b][c][d]=icnt;
}
for (int i=1;i<=m;i++)
{
len=read(s); read(t);
a=b=c=d=a1=b1=c1=d1=0;
for (int j=1;j<=len;j++)
{
a-=(s[j]=='A'),b-=(s[j]=='B'),c-=(s[j]=='C'),d-=(s[j]=='D');
a1+=(s[j]=='A'),b1+=(s[j]=='B'),c1+=(s[j]=='C'),d1+=(s[j]=='D');
}
for (int j=1;j<=len;j++)
a+=(t[j]=='A'),b+=(t[j]=='B'),c+=(t[j]=='C'),d+=(t[j]=='D');
for (int j=1;j<=icnt;j++)
if (S[j].a>=a1 && S[j].b>=b1 && S[j].c>=c1 && S[j].d>=d1)
{
a2=S[j].a+a; b2=S[j].b+b; c2=S[j].c+c; d2=S[j].d+d;
if (j!=back[a2][b2][c2][d2] && jud[j][back[a2][b2][c2][d2]]!=1)
add(j,back[a2][b2][c2][d2],++inum),jud[j][back[a2][b2][c2][d2]]=1;
//				add(j,back[a2][b2][c2][d2],++inum);
}
}
for (int i=1;i<=icnt;i++)
if (!pre[i])
Tarjan(i);
int tem=inum;
for (int i=1;i<=cnt;i++) head[i]=0; inum=0;
for (int p=1;p<=tem;p++)
if (scc[G[p].u]!=scc[G[p].v])
add(scc[G[p].u],scc[G[p].v],++inum);
Solve();
return 0;
}</span>