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Submission #390145

# Submission time Handle Problem Language Result Execution time Memory
390145 2021-04-15T13:00:14 Z talant117408 Star Trek (CEOI20_startrek) C++17
45 / 100
 112 ms 16684 KB 
/*
    Code written by Talant I.D.
*/
#include <bits/stdc++.h>
 
using namespace std;
 
typedef long long ll;
typedef pair <int, int> pii;
typedef pair <ll, ll> pll;
 
#define precision(n) fixed << setprecision(n)
#define pb push_back
#define ub upper_bound
#define lb lower_bound
#define mp make_pair
#define eps (double)1e-9
#define PI 2*acos(0.0)
#define endl "\n"
#define sz(v) int((v).size())
#define all(v) v.begin(),v.end()
#define rall(v) v.rbegin(),v.rend()
#define do_not_disturb ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define OK cout << "OK" << endl;
 
const int mod = 1e9+7;
 
ll mode(ll a) {
    a %= mod;
    if (a < 0) a += mod;
    return a;
}
 
ll subt(ll a, ll b) {
    return mode(mode(a)-mode(b));
}
 
ll add(ll a, ll b) {
    return mode(mode(a)+mode(b));
}
 
ll mult(ll a, ll b) {
    return mode(mode(a)*mode(b));
}
 
ll binpow(ll a, ll b) {
    ll res = 1;
    while (b) {
        if (b&1) res = mult(res, a);
        a = mult(a, a);
        b >>= 1;
    }
    return res;
}

const int N = 1e5+7;
int state[N], l, w, state_as_root[N];
int losing_children[N], critical[N], depth[N], par[N];
ll dp[N];
vector <int> graph[N];

bool dfs(int v, int p) {
	par[v] = p;
	depth[v] = depth[p]+1;
	int cnt = 0, children = 0;
	for (auto to : graph[v]) {
		if (to == p) continue;
		children++;
		dfs(to, v);
		cnt += (state[to] ? 1 : 0);
		if (state[to]) losing_children[v]++;
	}
	if (children == 0) state[v] = 1;
	else if (cnt) state[v] = 0;
	else state[v] = 1;
	return state[v];
}

void dfs2(int v, int p, int origin, int cnt = 0) {
	if (cnt == depth[v] && state[v]) critical[origin]++;
	if (state[v]) {
		for (auto to : graph[v]) {
			if (to == p) continue;
			dfs2(to, v, origin, cnt+1);
		}
	}
	else {
		for (auto to : graph[v]) {
			if (to == p) continue;
			if (state[to]) {
				dfs2(to, v, origin, (losing_children[v] == 1 ? cnt+1 : 0));
			}
		}
	}
}

void dfs3(int v, int p) {
	state_as_root[v] = state[v];
	if (state[v]) l++;
	else w++;
	for (auto to : graph[v]) {
		if (to == p) continue;
		if (state[v] == false && state[to] == true) {
			if (losing_children[v] == 1 && (state_as_root[par[v]] == false)) {
				losing_children[v]--;
				losing_children[to]++;
				state[v] = 1;
				state[to] = 0;
				dfs3(to, v);
				losing_children[v]++;
				losing_children[to]--;
				state[v] = 0;
				state[to] = 1;
			}
			else {
				dfs3(to, v);
			}
		}
		else {
			dfs3(to, v);
		}
	}
}

int main() {
	do_not_disturb
	
	int n;
	ll d;
	cin >> n >> d;
	for (int i = 0; i < n-1; i++) {
		int x, y;
		cin >> x >> y;
		graph[x].pb(y);
		graph[y].pb(x);
	}
	
	if (n == 2) {
		cout << binpow(2, d*2);
	}
	else if (d == 1) {
		depth[1] = -1;
		dfs(1, 1);
		dfs2(1, 1, 1);
		dfs3(1, 1);
		if (state_as_root[1]) cout << mult(critical[1], l);
		else cout << add(mult(n, w), mult(subt(n, critical[1]), l));
	}
	else if (d <= 1e5) {
		depth[1] = -1;
		dfs(1, 1);
		dfs3(1, 1);
		for (int i = 1; i <= n; i++) {
			depth[i] = -1;
			for (int j = 1; j <= n; j++) losing_children[j] = 0;
			dfs(i, i);
			dfs2(i, i, i);
		}
		dp[0] = l;
		ll E = 0;
		for (int i = 1; i <= n; i++) {
			if (state[i]) {
				E = subt(E, critical[i]);
			}
			else {
				E = add(E, critical[i]);
			}
		}
		for (int i = 1; i <= d; i++) {
			dp[i] = add(mult(l, binpow(n, 2*(d-i))), mult(E, dp[i-1]));
		}
		cout << (state[1] ? mult(dp[d-1], critical[1]) : subt(binpow(n, 2*d), mult(dp[d-1], critical[1]))) << 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 27 ms 2760 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 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

Subtask #3
8.0 / 8.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 2656 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 2680 KB Output is correct
5 Correct 2 ms 2640 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 2656 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 2680 KB Output is correct
5 Correct 2 ms 2640 KB Output is correct
6 Correct 2 ms 2636 KB Output is correct
7 Correct 2 ms 2764 KB Output is correct
8 Correct 2 ms 2764 KB Output is correct
9 Correct 2 ms 2764 KB Output is correct
10 Correct 3 ms 2636 KB Output is correct
11 Correct 2 ms 2764 KB Output is correct

Subtask #5
15.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 2656 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 2680 KB Output is correct
5 Correct 2 ms 2640 KB Output is correct
6 Correct 2 ms 2636 KB Output is correct
7 Correct 2 ms 2764 KB Output is correct
8 Correct 2 ms 2764 KB Output is correct
9 Correct 2 ms 2764 KB Output is correct
10 Correct 3 ms 2636 KB Output is correct
11 Correct 2 ms 2764 KB Output is correct
12 Correct 72 ms 11736 KB Output is correct
13 Correct 112 ms 16684 KB Output is correct
14 Correct 64 ms 8896 KB Output is correct
15 Correct 109 ms 9076 KB Output is correct
16 Correct 90 ms 8888 KB Output is correct

Subtask #6
0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 2656 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 2680 KB Output is correct
5 Correct 2 ms 2640 KB Output is correct
6 Correct 2 ms 2636 KB Output is correct
7 Correct 2 ms 2764 KB Output is correct
8 Correct 2 ms 2764 KB Output is correct
9 Correct 2 ms 2764 KB Output is correct
10 Correct 3 ms 2636 KB Output is correct
11 Correct 2 ms 2764 KB Output is correct
12 Correct 2 ms 2680 KB Output is correct
13 Incorrect 27 ms 2752 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 2656 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 2680 KB Output is correct
5 Correct 2 ms 2640 KB Output is correct
6 Correct 2 ms 2636 KB Output is correct
7 Correct 2 ms 2764 KB Output is correct
8 Correct 2 ms 2764 KB Output is correct
9 Correct 2 ms 2764 KB Output is correct
10 Correct 3 ms 2636 KB Output is correct
11 Correct 2 ms 2764 KB Output is correct
12 Correct 72 ms 11736 KB Output is correct
13 Correct 112 ms 16684 KB Output is correct
14 Correct 64 ms 8896 KB Output is correct
15 Correct 109 ms 9076 KB Output is correct
16 Correct 90 ms 8888 KB Output is correct
17 Correct 2 ms 2680 KB Output is correct
18 Incorrect 27 ms 2752 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 27 ms 2760 KB Output isn't correct