Submission #789152

#	Time	Username	Problem	Language	Result	Execution time	Memory
789152		MISM06	Sumtree (INOI20_sumtree)	C++14	10 / 100	148 ms	56040 KiB

Main

//0 1 1 0 1
//0 1 0 0 1
//1 0 0 1 1
//0 1 1 0 1
#include <bits/stdc++.h>
#pragma GCC optimize("Ofast,unroll-loops")
// #pragma GCC target("avx2")

using namespace std;

#define F 			first
#define S 			second
#define pb 			push_back
#define sze			size()
#define	all(x)		x.begin() , x.end()
#define wall__		cout << "--------------------------------------\n";
#define kids		int mid = (tl + tr) >> 1, cl = v << 1, cr = v << 1 | 1
#define file_io		freopen("input.cpp", "r", stdin); freopen("output.cpp", "w", stdout);

typedef long long ll;
typedef long double dl;
typedef pair < int , int > pii;
typedef pair < int , ll > pil;
typedef pair < ll , int > pli;
typedef pair < ll , ll > pll;
typedef pair < int , pii > piii;
typedef pair < ll, pll > plll;


const ll N = 2e5 + 10, M = 5e5 + 10;
const ll mod = 1e9 + 7;
const ll inf = 2e16;
const ll INF = 1e9 + 10;
const ll lg = 32;

ll fac[M], inv[M];
inline void add (ll &x, ll y) {
	x += y; if (x >= mod) x -= mod;
	if (x < 0) x += mod;
}
inline ll Sum (ll x, ll y) {
	x += y; if (x >= mod) x -= mod;
	if (x < 0) x += mod;
	return x;
}
inline ll mul (ll x, ll y) {
	x *= y; x %= mod; if (x < 0) x+= mod;
	return x;
}
inline ll pw (ll x, ll y) {
	ll res = 1;
	while(y) {
		if (y & 1) res = mul(res, x);
		x = mul(x, x);
		y >>= 1;
	}
	return res;
}
inline ll choose (ll x, ll y) {
	if (x < y || y < 0) return 0;
	return mul(fac[x], mul(inv[y], inv[x - y]));
}

ll n,  chp[N], par[N], hv[N], h[N], sub[N], chs[N], ANS;
ll a[N], st[N], en[N], timer = 0, ct[N], bit[N], rs[N], c0;
set < pii > s[N];
vector < int > g[N];
bool is[N];

inline ll read (int idx) {
	ll res = 0;
	for (; idx > 0; idx -= (idx & -idx)) res += bit[idx];
	return res;
}
inline void upd (int idx, ll val) {
	for (; idx <= n; idx += (idx & -idx)) 
		bit[idx] += val;
}
inline ll range (int l, int r) {
	return read(r) - read(l - 1);
}
void dfs0 (int v, int p) {
	par[v] = p;
	h[v] = h[p] + 1;
	st[v] = ++timer;
	sub[v] = 1;
	for (auto u : g[v]) {
		if (u == p) continue;
		dfs0(u, v);
		sub[v] += sub[u];
		if (sub[u] > sub[hv[v]]) hv[v] = u;
	}
	en[v] = timer;
}
void dfs (int v, int p) {
	chs[v] = v;
	for (auto u : g[v]) {
		if (u == p) continue;
		if (hv[v] == u) chp[u] = chp[v];
		else chp[u] = u;
		dfs(u, v);
		if (hv[v] == u) chs[v] = chs[u];
	}
}

void solve () {

	cin >> n >> a[1];
	for (int i = 1; i < n; i++) {
		int v, u; cin >> v >> u;
		g[v].pb(u); g[u].pb(v);
	}
	chp[1] = 1;
	dfs0(1, 0);
	dfs(1, 0);
	for (int i = 2; i <= n; i++) {
		ct[i] = 1;
		upd(st[i], 1);
	}
	ct[1] = n; upd(st[1], n);
	fill(rs, rs + N, -1);
	rs[1] = choose(a[1] + ct[1] - 1, ct[1] - 1);
	cout << rs[1] << '\n';
	int q; cin >> q;
	while(q--) {
		cout << 0 << '\n';
	}


}


int main() {
	ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	fac[0] = 1;
	for (int i = 1; i < M; i++) fac[i] = mul(fac[i - 1], i);
	inv[M - 1] = pw(fac[M - 1], mod - 2);
	for (int i = M - 2; i >= 0; --i) inv[i] = mul(inv[i + 1], i + 1);
	int t = 1;
	// cin >> t;
	while (t--) {solve();}
    return 0;
}
/*
*/
//shrek is love;

• Subtask 1: 10 / 10
• Subtask 2: 0 / 20
• Subtask 3: 0 / 20
• Subtask 4: 0 / 20
• Subtask 5: 0 / 30