oj.uz

답안 #579051

# 제출 시각 아이디 문제 언어 결과 실행 시간 메모리
579051 2022-06-18T10:53:53 Z piOOE Star Trek (CEOI20_startrek) C++17
45 / 100
 70 ms 20232 KB 
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

const int N = 100000, mod = 1e9 + 7;

int add(int a, int b) {
    return a + b < mod ? a + b : a + b - mod;
}

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

int binp(int a, ll p) {
    int ans = 1;
    for (; p > 0; p >>= 1, a = mul(a, a)) {
        if (p & 1) {
            ans = mul(ans, a);
        }
    }
    return ans;
}

int sub(int a, int b) {
    return a >= b ? a - b : a - b + mod;
}

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

vector<int> g[N];

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int n;
    ll d;
    cin >> n >> d;
    for (int i = 1; i < n; ++i) {
        int a, b;
        cin >> a >> b;
        --a, --b;
        g[a].push_back(b);
        g[b].push_back(a);
    }
    vector<bool> dp(n);
    vector<int> cntLoosing(n), c(n);

    function<void(int, int)> dfs1 = [&](int v, int p) {
        dp[v] = false;
        cntLoosing[v] = 0;
        int total = 0, only_loosing = 0;
        for (int to: g[v]) {
            if (to != p) {
                dfs1(to, v);
                if (!dp[to]) {
                    only_loosing += c[to];
                    ++cntLoosing[v];
                    dp[v] = true;
                }
                total += c[to];
            }
        }
        if (cntLoosing[v] > 1) {
            c[v] = 0;
        } else if (cntLoosing[v] == 1) {
            c[v] = only_loosing;
        } else {
            c[v] = total + 1;
        }
    };

    function<void(int, int)> dfs2 = [&](int v, int p) {
        int total = 0;
        for (int to : g[v]) {
            if (to != p) {
                total += c[to];
            }
        }
        dp[v] = cntLoosing[v];
        for (int to: g[v]) {
            if (to != p) {
                bool new_dp = true;
                if (dp[to]) {
                    new_dp = dp[v];
                } else if (cntLoosing[v] == 1) {
                    new_dp = false;
                }
                cntLoosing[to] += !new_dp;
                if (cntLoosing[to] > 1) {
                    c[to] = 0;
                } else if (cntLoosing[to] == 1) {
                    if (!new_dp) {
                        c[to] = total - c[v] + 1;
                    }
                } else {
                    c[to] = total;
                }
                dfs2(to, v);
            }
        }

    };

    dfs1(0, -1);
    dfs2(0, -1);

    int E = 0, L = 0;

    for (int i = 0; i < n; ++i) {
        if (dp[i]) {
            E = add(E, c[i]);
        } else {
            L += 1;
            E = sub(E, c[i]);
        }
//        cout << dp[i] << " ";
    }

//    cout << endl;

    int a = mul(n, n);

    int x = mul(L, mul(sub(binp(a, d), binp(E, d)), inv(sub(a, E))));

    int ans;

    if (dp[0]) {
        ans = mul(x, c[0]);
    } else {
        ans = sub(binp(a, d), mul(x, c[0]));
    }

    cout << sub(binp(a, d), ans);
    return 0;
}

Subtask #1
0.0 / 0.0

# 결과 실행 시간 메모리 Grader output
1 Correct 2 ms 2644 KB Output is correct
2 Incorrect 2 ms 2644 KB Output isn't correct
3 Halted 0 ms 0 KB -

Subtask #2
7.0 / 7.0

# 결과 실행 시간 메모리 Grader output
1 Correct 2 ms 2644 KB Output is correct
2 Correct 2 ms 2644 KB Output is correct
3 Correct 2 ms 2644 KB Output is correct
4 Correct 2 ms 2644 KB Output is correct
5 Correct 2 ms 2644 KB Output is correct

Subtask #3
8.0 / 8.0

# 결과 실행 시간 메모리 Grader output
1 Correct 2 ms 2676 KB Output is correct
2 Correct 2 ms 2676 KB Output is correct
3 Correct 2 ms 2644 KB Output is correct
4 Correct 2 ms 2668 KB Output is correct
5 Correct 2 ms 2644 KB Output is correct
6 Correct 2 ms 2644 KB Output is correct

Subtask #4
15.0 / 15.0

# 결과 실행 시간 메모리 Grader output
1 Correct 2 ms 2676 KB Output is correct
2 Correct 2 ms 2676 KB Output is correct
3 Correct 2 ms 2644 KB Output is correct
4 Correct 2 ms 2668 KB Output is correct
5 Correct 2 ms 2644 KB Output is correct
6 Correct 2 ms 2644 KB Output is correct
7 Correct 2 ms 2772 KB Output is correct
8 Correct 2 ms 2800 KB Output is correct
9 Correct 2 ms 2644 KB Output is correct
10 Correct 2 ms 2644 KB Output is correct
11 Correct 2 ms 2644 KB Output is correct

Subtask #5
15.0 / 15.0

# 결과 실행 시간 메모리 Grader output
1 Correct 2 ms 2676 KB Output is correct
2 Correct 2 ms 2676 KB Output is correct
3 Correct 2 ms 2644 KB Output is correct
4 Correct 2 ms 2668 KB Output is correct
5 Correct 2 ms 2644 KB Output is correct
6 Correct 2 ms 2644 KB Output is correct
7 Correct 2 ms 2772 KB Output is correct
8 Correct 2 ms 2800 KB Output is correct
9 Correct 2 ms 2644 KB Output is correct
10 Correct 2 ms 2644 KB Output is correct
11 Correct 2 ms 2644 KB Output is correct
12 Correct 70 ms 13504 KB Output is correct
13 Correct 69 ms 20232 KB Output is correct
14 Correct 43 ms 7676 KB Output is correct
15 Correct 62 ms 7776 KB Output is correct
16 Correct 52 ms 7784 KB Output is correct

Subtask #6
0 / 20.0

# 결과 실행 시간 메모리 Grader output
1 Correct 2 ms 2676 KB Output is correct
2 Correct 2 ms 2676 KB Output is correct
3 Correct 2 ms 2644 KB Output is correct
4 Correct 2 ms 2668 KB Output is correct
5 Correct 2 ms 2644 KB Output is correct
6 Correct 2 ms 2644 KB Output is correct
7 Correct 2 ms 2772 KB Output is correct
8 Correct 2 ms 2800 KB Output is correct
9 Correct 2 ms 2644 KB Output is correct
10 Correct 2 ms 2644 KB Output is correct
11 Correct 2 ms 2644 KB Output is correct
12 Correct 2 ms 2676 KB Output is correct
13 Incorrect 2 ms 2644 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 2676 KB Output is correct
2 Correct 2 ms 2676 KB Output is correct
3 Correct 2 ms 2644 KB Output is correct
4 Correct 2 ms 2668 KB Output is correct
5 Correct 2 ms 2644 KB Output is correct
6 Correct 2 ms 2644 KB Output is correct
7 Correct 2 ms 2772 KB Output is correct
8 Correct 2 ms 2800 KB Output is correct
9 Correct 2 ms 2644 KB Output is correct
10 Correct 2 ms 2644 KB Output is correct
11 Correct 2 ms 2644 KB Output is correct
12 Correct 70 ms 13504 KB Output is correct
13 Correct 69 ms 20232 KB Output is correct
14 Correct 43 ms 7676 KB Output is correct
15 Correct 62 ms 7776 KB Output is correct
16 Correct 52 ms 7784 KB Output is correct
17 Correct 2 ms 2676 KB Output is correct
18 Incorrect 2 ms 2644 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 2644 KB Output is correct
2 Incorrect 2 ms 2644 KB Output isn't correct
3 Halted 0 ms 0 KB -