# BZOJ 3167 [Heoi2013]Sao ——树形DP

BZOJ4824的强化版。

#include <map>
#include <cmath>
#include <queue>
#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
#define F(i,j,k) for (ll i=j;i<=k;++i)
#define D(i,j,k) for (ll i=j;i>=k;--i)
#define ll long long
#define mp make_pair
#define maxn 1050
const ll md=1000000007;

ll h[maxn<<1],to[maxn<<1],ne[maxn<<1],en=0,n;
ll siz[maxn],tmp[maxn],w[maxn],lim[maxn];
ll dp[maxn][maxn],c[maxn][maxn],suf[maxn][maxn],pre[maxn][maxn];
char s[maxn];
{
to[en]=b;ne[en]=h[a];w[en]=c;h[a]=en++;
}

ll C(ll n,ll m)
{
if (n<0||m<0) return 0;
return c[n][m];
}

void Tree_DP(ll o,ll fa)
{
dp[o][1]=1;siz[o]=1;
for (ll i=h[o];i>=0;i=ne[i])
if (to[i]!=fa){
Tree_DP(to[i],o);
F(j,0,siz[o]+siz[to[i]]+2) tmp[j]=0;
if (w[i]==1)
{
F(j,1,siz[o])
if (dp[o][j]) F(_j,j,j+siz[to[i]]-1)
tmp[_j]+=(((dp[o][j]*suf[to[i]][_j-j+1])%md*C(_j-1,j-1))%md*C(siz[o]+siz[to[i]]-_j,siz[o]-j))%md,tmp[_j]%=md;
}
else
{
F(j,1,siz[o])
if (dp[o][j]) F(_j,j+1,siz[to[i]]+j)
tmp[_j]+=(((dp[o][j]*((suf[to[i]][1]-suf[to[i]][_j-j+1])%md+md))%md*C(_j-1,j-1))%md*C(siz[o]+siz[to[i]]-_j,siz[o]-j))%md,tmp[_j]%=md;
}
siz[o]+=siz[to[i]];
F(j,0,siz[o]) dp[o][j]=(tmp[j]%md+md)%md;
}
suf[o][siz[o]]=dp[o][siz[o]];
D(i,siz[o],1) suf[o][i]=(suf[o][i+1]+dp[o][i])%md;
}

void Finout()
{
freopen("in.txt","r",stdin);
freopen("wa.txt","w",stdout);
}

ll t;

int main()
{
scanf("%lld",&t);
c[1][0]=1;c[1][1]=1;c[0][0]=1;
F(i,2,maxn-1)
{
c[i][0]=1;
F(j,1,maxn-1) c[i][j]=(c[i-1][j]+c[i-1][j-1])%md;
}
while (t--)
{
memset(dp,0,sizeof dp);
memset(suf,0,sizeof suf);
memset(h,-1,sizeof h);en=0;
scanf("%lld",&n);
F(i,2,n)
{
ll a,b,c;
scanf("%lld",&a);
a++;
scanf("%s",s);
scanf("%lld",&b);b++;
switch(s[0])
{
case '<':c=1;break;
case '>':c=-1;break;
}