[Tarjan缩点 拓扑序DP] SRM 499 1000pts

题目大意:

题解：

<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[N];int n,m;int icnt,back[L][L][L][L];ll val[N];struct Stack{    int s[N],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[N],inum;bitset<N> jud[N];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[N];int clk,pre[N],low[N],scc[N];#define V G[p].vinline 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[N];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[N];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[n]/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>