oj.uz

답안 #459114

# 제출 시각 아이디 문제 언어 결과 실행 시간 메모리
459114 2021-08-08T08:49:50 Z AmShZ Star Trek (CEOI20_startrek) C++11
38 / 100
 125 ms 18428 KB 
//khodaya khodet komak kon
# include <bits/stdc++.h>

using namespace std;

typedef long long                                        ll;
typedef long double                                      ld;
typedef pair <int, int>                                  pii;
typedef pair <pii, int>                                  ppi;
typedef pair <int, pii>                                  pip;
typedef pair <pii, pii>                                  ppp;
typedef pair <ll, ll>                                    pll;

# define A                                               first
# define B                                               second
# define endl                                            '\n'
# define sep                                             ' '
# define all(x)                                          x.begin(), x.end()
# define kill(x)                                         return cout << x << endl, 0
# define SZ(x)                                           int(x.size())
# define lc                                              id << 1
# define rc                                              id << 1 | 1
# define fast_io                                         ios::sync_with_stdio(0);cin.tie(0); cout.tie(0);

ll power(ll a, ll b, ll md) {return (!b ? 1 : (b & 1 ? a * power(a * a % md, b / 2, md) % md : power(a * a % md, b / 2, md) % md));}

const int xn = 1e5 + 10;
const int xm = - 20 + 10;
const int sq = 320;
const int inf = 1e9 + 10;
const ll INF = 1e18 + 10;
const ld eps = 1e-15;
const int mod = 1e9 + 7;//998244353;
const int base = 257;

int n, dp[2][xn], sz[2][xn], par[xn], ans;
bool f[2][xn];
ll D;
vector <int> adj[xn];

void DFS(int v, int p = - 1){
	sz[0][v] = 1;
	int ted = 0;
	for (int u : adj[v]){
		if (u == p)
			continue;
		par[u] = v;
		DFS(u, v);
		f[0][v] |= !(f[0][u]);
		sz[0][v] += sz[0][u];
		ted += !f[0][u];
	}
	dp[0][v] = sz[0][v];
	for (int u : adj[v])
		if (u != p && ted == !f[0][u])
			dp[0][v] -= dp[0][u];
}
void DFS2(int v, int p = - 1){
	int ted = !f[1][v];
	for (int u : adj[v])
		if (u != p)
			ted += !f[0][u], sz[1][v] += sz[0][u];
	++ sz[1][v];
	int sum0 = 0, sum1 = 0;
	for (int u : adj[v]){
		if (u == p)
			continue;
		sz[1][u] = sz[1][v] - sz[0][u];
		dp[1][u] = sz[1][u];
		f[1][u] = (0 < ted - !f[0][u]);
		if (f[0][u])
			sum1 += dp[0][u];
		else
			sum0 += dp[0][u];
	}
	if (f[1][v])
		sum1 += dp[1][v];
	else
		sum0 += dp[1][v];
	for (int u : adj[v]){
		if (u == p)
			continue;
		if (f[0][u])
			sum1 -= dp[0][u];
		else
			sum0 -= dp[0][u];
		if (ted - !f[0][u] == 0)
			dp[1][u] -= sum1;
		else if (ted - !f[0][u] == 1)
			dp[1][u] -= sum0;
		if (f[0][u])
			sum1 += dp[0][u];
		else
			sum0 += dp[0][u];
		DFS2(u, v);
	}
}

struct matrix{
    int a[2][2];
    matrix operator * (const matrix &t){
        matrix r;
        for (int i = 0; i < 2; ++ i)
        	for (int j = 0; j < 2; ++ j)
        		for (int k = 0; k < 2; ++ k)
        			r.a[i][k] = (r.a[i][k] + 1ll * a[i][j] * t.a[!j][k] % mod) % mod;
        return r;
    }
};
matrix Pow(matrix a, ll b){
    matrix res = a;
    if (b < 0)
    	return res;
    for (; b; b = b >> 1){
        if (b & 1)
            res = res * a;
        a = a * a;
    }
    return res;
}

int main(){
	fast_io;

	cin >> n >> D;
	for (int i = 0; i < n - 1; ++ i){
		int v, u;
		cin >> v >> u;
		adj[v].push_back(u);
		adj[u].push_back(v);
	}
	DFS(1);
	f[1][1] = 1;
	DFS2(1);
	matrix M;
	for (int i = 0; i < 2; ++ i)
		for (int j = 0; j < 2; ++ j)
			M.a[i][j] = 0;
	pii last;
	for (int v = 1; v <= n; ++ v){
		bool fl = !f[1][v];
		int ted = !f[1][v];
		for (int u : adj[v]){
			if (u == par[v])
				continue;
			fl |= !f[0][u];
			ted += !f[0][u];
		}
		int val = n;
		if (ted == !f[1][v])
			val -= dp[1][v];
		for (int u : adj[v])
			if (u != par[v] && ted == !f[0][u])
				val -= dp[0][u];
		M.a[1][1] = (M.a[1][1] + val) % mod;
		M.a[0][1] += (M.a[0][1] + n - val) % mod;
		if (fl)
			M.a[1][0] = (M.a[1][0] + n) % mod;
		else
			M.a[0][0] = (M.a[0][0] + n) % mod;
		if (v == 1)
			last = {fl, val};
	}
	M = Pow(M, D - 1);
	if (last.A)
		ans = (ans + 1ll * n * M.a[1][0] % mod) % mod;
	ans = (ans + 1ll * last.B * M.a[0][0] % mod) % mod;
	ans = 1ll * ans * power(n, mod - 2, mod) % mod;
	cout << ans << endl;

	return 0;
}

Subtask #1
0.0 / 0.0

# 결과 실행 시간 메모리 Grader output
1 Correct 2 ms 2636 KB Output is correct
2 Incorrect 3 ms 2636 KB Output isn't correct

Subtask #2
0 / 7.0

# 결과 실행 시간 메모리 Grader output
1 Incorrect 2 ms 2636 KB Output isn't correct
2 Halted 0 ms 0 KB -

Subtask #3
8.0 / 8.0

# 결과 실행 시간 메모리 Grader output
1 Correct 2 ms 2636 KB Output is correct
2 Correct 2 ms 2636 KB Output is correct
3 Correct 2 ms 2636 KB Output is correct
4 Correct 2 ms 2668 KB Output is correct
5 Correct 2 ms 2636 KB Output is correct
6 Correct 3 ms 2636 KB Output is correct

Subtask #4
15.0 / 15.0

# 결과 실행 시간 메모리 Grader output
1 Correct 2 ms 2636 KB Output is correct
2 Correct 2 ms 2636 KB Output is correct
3 Correct 2 ms 2636 KB Output is correct
4 Correct 2 ms 2668 KB Output is correct
5 Correct 2 ms 2636 KB Output is correct
6 Correct 3 ms 2636 KB Output is correct
7 Correct 2 ms 2764 KB Output is correct
8 Correct 2 ms 2804 KB Output is correct
9 Correct 2 ms 2764 KB Output is correct
10 Correct 2 ms 2764 KB Output is correct
11 Correct 3 ms 2672 KB Output is correct

Subtask #5
15.0 / 15.0

# 결과 실행 시간 메모리 Grader output
1 Correct 2 ms 2636 KB Output is correct
2 Correct 2 ms 2636 KB Output is correct
3 Correct 2 ms 2636 KB Output is correct
4 Correct 2 ms 2668 KB Output is correct
5 Correct 2 ms 2636 KB Output is correct
6 Correct 3 ms 2636 KB Output is correct
7 Correct 2 ms 2764 KB Output is correct
8 Correct 2 ms 2804 KB Output is correct
9 Correct 2 ms 2764 KB Output is correct
10 Correct 2 ms 2764 KB Output is correct
11 Correct 3 ms 2672 KB Output is correct
12 Correct 125 ms 13408 KB Output is correct
13 Correct 119 ms 18428 KB Output is correct
14 Correct 116 ms 9008 KB Output is correct
15 Correct 100 ms 9204 KB Output is correct
16 Correct 84 ms 9132 KB Output is correct

Subtask #6
0 / 20.0

# 결과 실행 시간 메모리 Grader output
1 Correct 2 ms 2636 KB Output is correct
2 Correct 2 ms 2636 KB Output is correct
3 Correct 2 ms 2636 KB Output is correct
4 Correct 2 ms 2668 KB Output is correct
5 Correct 2 ms 2636 KB Output is correct
6 Correct 3 ms 2636 KB Output is correct
7 Correct 2 ms 2764 KB Output is correct
8 Correct 2 ms 2804 KB Output is correct
9 Correct 2 ms 2764 KB Output is correct
10 Correct 2 ms 2764 KB Output is correct
11 Correct 3 ms 2672 KB Output is correct
12 Correct 2 ms 2636 KB Output is correct
13 Incorrect 2 ms 2680 KB Output isn't correct
14 Halted 0 ms 0 KB -

Subtask #7
0 / 20.0

# 결과 실행 시간 메모리 Grader output
1 Correct 2 ms 2636 KB Output is correct
2 Correct 2 ms 2636 KB Output is correct
3 Correct 2 ms 2636 KB Output is correct
4 Correct 2 ms 2668 KB Output is correct
5 Correct 2 ms 2636 KB Output is correct
6 Correct 3 ms 2636 KB Output is correct
7 Correct 2 ms 2764 KB Output is correct
8 Correct 2 ms 2804 KB Output is correct
9 Correct 2 ms 2764 KB Output is correct
10 Correct 2 ms 2764 KB Output is correct
11 Correct 3 ms 2672 KB Output is correct
12 Correct 125 ms 13408 KB Output is correct
13 Correct 119 ms 18428 KB Output is correct
14 Correct 116 ms 9008 KB Output is correct
15 Correct 100 ms 9204 KB Output is correct
16 Correct 84 ms 9132 KB Output is correct
17 Correct 2 ms 2636 KB Output is correct
18 Incorrect 2 ms 2680 KB Output isn't correct
19 Halted 0 ms 0 KB -

Subtask #8
0 / 15.0

# 결과 실행 시간 메모리 Grader output
1 Correct 2 ms 2636 KB Output is correct
2 Incorrect 3 ms 2636 KB Output isn't correct