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| #include <cstdio>
#include <cstring>
#define maxN 110
#define maxM 20010
#define mod 1000000007LL
struct node{ long long x, y, g; } b[maxN << 1];
long long su[maxN][maxM], f[maxN][maxM], son[maxN][maxN], h[maxN];
long long len = 0, n = 0, m = 0, k = 0, p = 0;
long long min (long long x, long long y)
{
return x < y ? x : y;
}
long long max (long long x, long long y)
{
return x > y ? x : y;
}
void ins (long long x, long long y)
{
len++;
b[len].x = x;
b[len].y = y;
b[len].g = h[x];
h[x] = len;
}
void dfs (long long x, long long fa)
{
for(long long i = h[x];i;i = b[i].g)
{
long long y = b[i].y;
if(y != fa)
{
son[x][++son[x][0]] = y;
dfs(y, x);
}
}
}
long long sum (long long x, long long K)
{
long long res = 0;
long long t = min(p, K);
res = su[x][t] % mod;
long long c = K - (m - p);
if(c > 0)
{
K -= c;
res += (su[x][p] + mod - su[x][p - c]) % mod;
res %= mod;
}
K -= t;
res += f[x][p] * K;
res %= mod;
return res;
}
void dp (long long x)
{
if(!son[x][0])
{
for(long long i = 1;i <= m; i++)
{
f[x][i] = 1;
su[x][i] = su[x][i - 1] + f[x][i];
su[x][i] %= mod;
}
return ;
}
for(long long i = 1;i <= son[x][0]; i++)
{
dp(son[x][i]);
}
for(long long j = 1;j <= m; j++)
{
f[x][j] = 1;
bool flag = false;
for(long long i = 1;i <= son[x][0]; i++)
{
long long da = 0;
if(j > k)
{
flag = true;
da += su[son[x][i]][j - k];
da %= mod;
}
long long L = (j + k) + (j - k == j + k);
if(L <= m)
{
flag = true;
da += (su[son[x][i]][m] + mod - su[son[x][i]][L - 1]) % mod;
da %= mod;
}
f[x][j] *= da;
f[x][j] %= mod;
}
f[x][j] *= flag;
su[x][j] = (su[x][j - 1] + f[x][j]) % mod;
}
}
void dp2 (long long x)
{
if(!son[x][0])
{
for(long long i = 1;i <= p; i++)
{
f[x][i] = 1;
su[x][i] = su[x][i - 1] + f[x][i];
su[x][i] %= mod;
}
return ;
}
for(long long i = 1;i <= son[x][0]; i++)
{
dp2(son[x][i]);
}
for(long long j = 1;j <= p; j++)
{
f[x][j] = 1;
bool flag = false;
for(long long i = 1;i <= son[x][0]; i++)
{
long long da = 0;
if(j > k)
{
flag = true;
da += sum(son[x][i], j - k);
da %= mod;
}
long long L = (j + k) + (j - k == j + k);
if(L <= m)
{
flag = true;
da += (sum(son[x][i], m) + mod - sum(son[x][i], L - 1)) % mod;
da %= mod;
}
f[x][j] *= da;
f[x][j] %= mod;
}
f[x][j] *= flag;
su[x][j] = (su[x][j - 1] + f[x][j]) % mod;
}
}
int main ()
{
long long T = 0;
scanf("%lld", &T);
while(T--)
{
memset(f, 0, sizeof(f));
scanf("%lld %lld %lld", &n, &m, &k);
for(long long i = 1;i <= n - 1; i++)
{
long long x = 0, y = 0;
scanf("%lld %lld", &x, &y);
ins(x, y);
ins(y, x);
}
dfs(1, 0);
p = m;
if(m > 2 * (n - 1) * k)
{
p = (n - 1) * k + 1;
dp2(1);
}
else
{
dp(1);
}
long long ans = 0;
for(long long i = 1;i <= p; i++)
{
ans += f[1][i];
ans %= mod;
}
if(m > 2 * (n - 1) * k)
{
ans = ans * 2 % mod;
ans = (ans + f[1][p] * (m - 2 * p)) % mod;
}
printf("%lld\n", ans);
len = 0;
for(long long i = 1;i <= n; i++)
{
h[i] = 0;
son[i][0] = 0;
}
}
return 0;
}
|