挣扎十几分钟了求调UB qwq（不开O2AC开O2RE）

#include <cstdio>
#include <cstring>
const int N = 2e3 + 10, mod = 1e9 + 7;
typedef long long ll; ll C[N][N];
struct edge{ int v, next, w; }E[N << 1]; int p[N], cnt;
inline void init() { memset(p, -1, sizeof p); cnt = 0; }
inline void insert(int u, int v, int w)
{ E[cnt].w = w; E[cnt].v = v; E[cnt].next = p[u]; p[u] = cnt++; }
int size[N]; ll f[N][N], g[N];
void dfs(int u, int fa)
{
    size[u] = 1; f[u][1] = 1;
    for (int t = p[u], v; t + 1; t = E[t].next)
    {
        v = E[t].v; if (v == fa) continue;
        dfs(v, u);
        for (int i = 1; i <= size[u]; i++) g[i] = f[u][i], f[u][i] = 0;
        if (E[t].w)
        {
            //这里0是因为前面有可能一个都没有
            //<是因为v在u后面，v子树不可能全部都在u前面 
            for (int i = 1; i <= size[u]; i++)
                for (int j = 0; j < size[v]; j++)
                    f[u][i + j] = (f[u][i + j] + 
                    C[size[u] + size[v] - i - j][size[v] - j] * C[i + j - 1][j] % mod
                    * g[i] % mod * (f[v][size[v]] - f[v][j] + mod) % mod) % mod;
        }
        else
        {
            //这里1是因为前面至少有个v
            //<=是因为v就在u前面，v子树有可能全在u前面 
            for (int i = 1; i <= size[u]; i++)
                for (int j = 1; j <= size[v]; j++)
                    f[u][i + j] = (f[u][i + j] + 
                    C[size[u] + size[v] - i - j][size[v] - j] * C[i + j - 1][j] % mod
                    * g[i] % mod * f[v][j] % mod) % mod;
        }
        size[u] += size[v];
    }
    for (int i = 1; i <= size[u]; i++) f[u][i] = (f[u][i] + f[u][i - 1]) % mod;
}
int main()
{
    int T, n; scanf("%d", &T); char opt[5]; C[0][0] = 1;
    for (int i = 1; i <= N; i++)
    {
        C[i][0] = 1;
        for (int j = 1; j <= i; j++)
            C[i][j] = (C[i - 1][j] + C[i - 1][j - 1]) % mod;
    }   
    while (T--)
    {
        init(); scanf("%d", &n);
        for (int i = 1, x, y; i < n; i++)
        {
            scanf("%d", &x); ++x; scanf("%s", opt); scanf("%d", &y); ++y;
            insert(x, y, opt[0] == '<'); insert(y, x, opt[0] == '>');
        }
        dfs(1, 0);
        printf("%lld\n", f[1][n]);
        for (int i = 1; i <= n; i++)
        {
            for (int j = 1; j <= n; j++) f[i][j] = 0;
            size[i] = 0;
        }   
    }
    return 0;
}

P4099 （虽然不知道为什么调UB要看原题但还是放上吧）

当然也有可能不是UB，求大佬指点/kel 自己实在找不出来了