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Submission #579076

# Submission time Handle Problem Language Result Execution time Memory
579076 2022-06-18T11:14:01 Z piOOE Star Trek (CEOI20_startrek) C++17
45 / 100
 92 ms 20300 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), gg(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]) {
            total += gg[to];
        }
        dp[v] = cntLoosing[v];
        for (int to: g[v]) {
            if (to != p) {
                int new_gg = gg[v];
                if (cntLoosing[v] == 1 && !dp[to]) {
                    new_gg = 0;
                } else if (cntLoosing[v] == 0) {
                    new_gg -= c[to];
                }
                bool new_dp = dp[v];
                if (!dp[to] && 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] = new_gg + 1;
                    }
                } else {
                    c[to] = new_gg + c[to];
                }
                dfs2(to, v);
            }
        }

    };

    dfs1(0, -1);

    gg = c;

    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

# Verdict Execution time Memory Grader output
1 Correct 2 ms 2672 KB Output is correct
2 Incorrect 2 ms 2700 KB Output isn't correct
3 Halted 0 ms 0 KB -

Subtask #2
7.0 / 7.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 2664 KB Output is correct
2 Correct 2 ms 2644 KB Output is correct
3 Correct 2 ms 2668 KB Output is correct
4 Correct 3 ms 2644 KB Output is correct
5 Correct 2 ms 2672 KB Output is correct

Subtask #3
8.0 / 8.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 2676 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 2596 KB Output is correct
5 Correct 2 ms 2668 KB Output is correct
6 Correct 2 ms 2644 KB Output is correct

Subtask #4
15.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 2676 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 2596 KB Output is correct
5 Correct 2 ms 2668 KB Output is correct
6 Correct 2 ms 2644 KB Output is correct
7 Correct 2 ms 2772 KB Output is correct
8 Correct 3 ms 2772 KB Output is correct
9 Correct 3 ms 2672 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

# Verdict Execution time Memory Grader output
1 Correct 2 ms 2676 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 2596 KB Output is correct
5 Correct 2 ms 2668 KB Output is correct
6 Correct 2 ms 2644 KB Output is correct
7 Correct 2 ms 2772 KB Output is correct
8 Correct 3 ms 2772 KB Output is correct
9 Correct 3 ms 2672 KB Output is correct
10 Correct 2 ms 2644 KB Output is correct
11 Correct 2 ms 2644 KB Output is correct
12 Correct 68 ms 13552 KB Output is correct
13 Correct 72 ms 20300 KB Output is correct
14 Correct 43 ms 8040 KB Output is correct
15 Correct 92 ms 7932 KB Output is correct
16 Correct 57 ms 7936 KB Output is correct

Subtask #6
0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 2676 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 2596 KB Output is correct
5 Correct 2 ms 2668 KB Output is correct
6 Correct 2 ms 2644 KB Output is correct
7 Correct 2 ms 2772 KB Output is correct
8 Correct 3 ms 2772 KB Output is correct
9 Correct 3 ms 2672 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 2644 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

# Verdict Execution time Memory Grader output
1 Correct 2 ms 2676 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 2596 KB Output is correct
5 Correct 2 ms 2668 KB Output is correct
6 Correct 2 ms 2644 KB Output is correct
7 Correct 2 ms 2772 KB Output is correct
8 Correct 3 ms 2772 KB Output is correct
9 Correct 3 ms 2672 KB Output is correct
10 Correct 2 ms 2644 KB Output is correct
11 Correct 2 ms 2644 KB Output is correct
12 Correct 68 ms 13552 KB Output is correct
13 Correct 72 ms 20300 KB Output is correct
14 Correct 43 ms 8040 KB Output is correct
15 Correct 92 ms 7932 KB Output is correct
16 Correct 57 ms 7936 KB Output is correct
17 Correct 2 ms 2644 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

# Verdict Execution time Memory Grader output
1 Correct 2 ms 2672 KB Output is correct
2 Incorrect 2 ms 2700 KB Output isn't correct
3 Halted 0 ms 0 KB -