Submission #624199

#	Time	Username	Problem	Language	Result	Execution time	Memory
624199		Arinoor	Sumtree (INOI20_sumtree)	C++17	100 / 100	617 ms	65628 KiB

Main

#include <bits/stdc++.h>
using namespace std;

#define pb				push_back
#define mp				make_pair
#define fi				first
#define se				second
#define all(x)			x.begin(), x.end()
#define bug(x)			cout << #x << " : " << x << '\n'
#define ios				ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0)

typedef long long ll;
typedef pair<int, int> pii;

const int maxn = 2e5 + 10;
const int maxlg = 19;
const int maxf = 1e6 + 10;
const int mod = 1e9 + 7;
const int inf = 1e9 + 10;

int n, fact[maxf], invfact[maxf];
int val[maxn], tag[maxn];
int par[maxn][maxlg], sz[maxn], st[maxn], ed[maxn], tme = 1;
ll fenC[maxn], fenS[maxn], fenP[maxn];
vector<int> G[maxn];

int add(int a, int b){
	int c = a + b;
	if(c >= mod) c -= mod;
	if(c < 0) c += mod;
	return c;
}

int mul(int a, int b){
	return 1ll * a * b % mod;
}

int pwr(int a, int b){
	int res = 1;
	for(; b; b >>= 1, a = mul(a, a)) if(b & 1) res = mul(res, a);
	return res;
}

int inv(int a){
	return pwr(a, mod - 2);
}

int C(int a, ll b){
	if(a > b)
		return 0;
	return mul(fact[b], mul(invfact[a], invfact[b - a]));
}

void update_fact(){
	fact[0] = 1;
	for(int i = 1; i < maxf; i ++)
		fact[i] = mul(fact[i - 1], i);
	invfact[maxf - 1] = inv(fact[maxf - 1]);
	for(int i = maxf - 2; ~i; i --)
		invfact[i] = mul(invfact[i + 1], i + 1);
}

void add(ll *fen, int i, ll x){
	for(; i <= n; i += i & -i)
		fen[i] += x;
}

ll get(ll *fen, int i){
	ll res = 0;
	for(; i; i -= i & -i)
		res += fen[i];
	return res;
}

ll get(ll *fen, int l, int r){
	return get(fen, r) - get(fen, l);
}

void dfs(int v, int p = 0){
	par[v][0] = p;
	for(int i = 1; i < maxlg and par[v][i - 1]; i ++)
		par[v][i] = par[par[v][i - 1]][i - 1];
	st[v] = tme;
	sz[v] = 1;
	for(int u : G[v]){
		if(u ^ p){
			tme ++;
			dfs(u, v);
			sz[v] += sz[u];
		}
	}
	ed[v] = tme;
}

int get_val(int v){
	int cnt = sz[v] - get(fenC, st[v], ed[v]);
	ll sum = tag[v] - get(fenS, st[v], ed[v]);
	return C(cnt - 1, cnt + sum - 1);
}

int find(int v){
	int x = get(fenP, st[v]);
	for(int i = maxlg - 1; ~i; i --){
		int u = par[v][i];
		if(!u) continue;
		if(get(fenP, st[u]) == x)
			v = u;
	}
	return par[v][0];
}

int main(){
	ios;
	update_fact();
	int r;
	cin >> n >> r;
	for(int i = 0; i < n - 1; i ++){
		int u, v;
		cin >> u >> v;
		G[u].pb(v);
		G[v].pb(u);
	}
	dfs(1);
	memset(tag, -1, sizeof tag);
	tag[1] = r;
	add(fenP, st[1] + 1, 1); add(fenP, ed[1] + 1, -1);
	fill_n(val, maxn, 1);
	int ans = val[1] = get_val(1);
	cout << ans << '\n';
	int q; cin >> q;
	int Cnt = 0;
	while(q--){
		int t, v;
		cin >> t >> v;
		int p = find(v);
		if(t == 1){
			cin >> tag[v];
			int cnt = sz[v] - get(fenC, st[v], ed[v]);
			ll sum = tag[v] - get(fenS, st[v], ed[v]);
			add(fenC, st[v], cnt);
			add(fenS, st[v], sum);
			add(fenC, st[p], -cnt);
			add(fenS, st[p], -sum);
			add(fenP, st[v] + 1, 1); add(fenP, ed[v] + 1, -1);
			val[v] = get_val(v);
			if(val[v])
				ans = mul(ans, val[v]);
			else
				Cnt ++;
			if(inv(val[p]))
				ans = mul(ans, inv(val[p]));
			else
				Cnt --;
			val[p] = get_val(p);
			if(val[p])
				ans = mul(ans, val[p]);
			else
				Cnt ++;
		}
		else{
			int cnt = sz[v] - get(fenC, st[v], ed[v]);
			ll sum = tag[v] - get(fenS, st[v], ed[v]);
			add(fenC, st[v], -cnt);
			add(fenS, st[v], -sum);
			add(fenC, st[p], cnt);
			add(fenS, st[p], sum);
			add(fenP, st[v] + 1, -1); add(fenP, ed[v] + 1, 1);
			if(inv(val[v]))
				ans = mul(ans, inv(val[v]));
			else
				Cnt --;
			val[v] = 1;
			if(inv(val[p]))
				ans = mul(ans, inv(val[p]));
			else
				Cnt --;
			val[p] = get_val(p);
			if(val[p])
				ans = mul(ans, val[p]);
			else
				Cnt ++;
			tag[v] = -1;
		}
		if(Cnt)
			cout << "0\n";
		else
			cout << ans << '\n';
	}
}

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