oj.uz

Submission #459128

# Submission time Handle Problem Language Result Execution time Memory
459128 2021-08-08T08:55:28 Z AmShZ Star Trek (CEOI20_startrek) C++11
45 / 100
 103 ms 17264 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)
        		r.a[i][j] = 0;
        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

# Verdict Execution time Memory Grader output
1 Correct 2 ms 2636 KB Output is correct
2 Incorrect 2 ms 2636 KB Output isn't correct

Subtask #2
7.0 / 7.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 2636 KB Output is correct
2 Correct 2 ms 2680 KB Output is correct
3 Correct 2 ms 2636 KB Output is correct
4 Correct 2 ms 2636 KB Output is correct
5 Correct 2 ms 2636 KB Output is correct

Subtask #3
8.0 / 8.0

# Verdict Execution time Memory 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 2636 KB Output is correct
5 Correct 2 ms 2636 KB Output is correct
6 Correct 2 ms 2636 KB Output is correct

Subtask #4
15.0 / 15.0

# Verdict Execution time Memory 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 2636 KB Output is correct
5 Correct 2 ms 2636 KB Output is correct
6 Correct 2 ms 2636 KB Output is correct
7 Correct 2 ms 2764 KB Output is correct
8 Correct 3 ms 2764 KB Output is correct
9 Correct 2 ms 2636 KB Output is correct
10 Correct 2 ms 2636 KB Output is correct
11 Correct 2 ms 2636 KB Output is correct

Subtask #5
15.0 / 15.0

# Verdict Execution time Memory 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 2636 KB Output is correct
5 Correct 2 ms 2636 KB Output is correct
6 Correct 2 ms 2636 KB Output is correct
7 Correct 2 ms 2764 KB Output is correct
8 Correct 3 ms 2764 KB Output is correct
9 Correct 2 ms 2636 KB Output is correct
10 Correct 2 ms 2636 KB Output is correct
11 Correct 2 ms 2636 KB Output is correct
12 Correct 95 ms 12228 KB Output is correct
13 Correct 92 ms 17264 KB Output is correct
14 Correct 75 ms 8128 KB Output is correct
15 Correct 103 ms 8024 KB Output is correct
16 Correct 92 ms 7876 KB Output is correct

Subtask #6
0 / 20.0

# Verdict Execution time Memory 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 2636 KB Output is correct
5 Correct 2 ms 2636 KB Output is correct
6 Correct 2 ms 2636 KB Output is correct
7 Correct 2 ms 2764 KB Output is correct
8 Correct 3 ms 2764 KB Output is correct
9 Correct 2 ms 2636 KB Output is correct
10 Correct 2 ms 2636 KB Output is correct
11 Correct 2 ms 2636 KB Output is correct
12 Correct 2 ms 2636 KB Output is correct
13 Incorrect 3 ms 2636 KB Output isn't correct
14 Halted 0 ms 0 KB -

Subtask #7
0 / 20.0

# Verdict Execution time Memory 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 2636 KB Output is correct
5 Correct 2 ms 2636 KB Output is correct
6 Correct 2 ms 2636 KB Output is correct
7 Correct 2 ms 2764 KB Output is correct
8 Correct 3 ms 2764 KB Output is correct
9 Correct 2 ms 2636 KB Output is correct
10 Correct 2 ms 2636 KB Output is correct
11 Correct 2 ms 2636 KB Output is correct
12 Correct 95 ms 12228 KB Output is correct
13 Correct 92 ms 17264 KB Output is correct
14 Correct 75 ms 8128 KB Output is correct
15 Correct 103 ms 8024 KB Output is correct
16 Correct 92 ms 7876 KB Output is correct
17 Correct 2 ms 2636 KB Output is correct
18 Incorrect 3 ms 2636 KB Output isn't correct
19 Halted 0 ms 0 KB -

Subtask #8
0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 2636 KB Output is correct
2 Incorrect 2 ms 2636 KB Output isn't correct