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Submission #579068

# Submission time Handle Problem Language Result Execution time Memory
579068 2022-06-18T11:09:52 Z piOOE Star Trek (CEOI20_startrek) C++17
45 / 100
 90 ms 19824 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] = gg[v] + 1;
                    }
                } else {
                    c[to] = gg[v] + 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 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

# 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 2672 KB Output is correct
4 Correct 2 ms 2644 KB Output is correct
5 Correct 3 ms 2672 KB Output is correct

Subtask #3
8.0 / 8.0

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

Subtask #4
15.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 1 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
6 Correct 2 ms 2644 KB Output is correct
7 Correct 3 ms 2764 KB Output is correct
8 Correct 2 ms 2772 KB Output is correct
9 Correct 2 ms 2668 KB Output is correct
10 Correct 2 ms 2644 KB Output is correct
11 Correct 2 ms 2672 KB Output is correct

Subtask #5
15.0 / 15.0

# Verdict Execution time Memory Grader output
1 Correct 1 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
6 Correct 2 ms 2644 KB Output is correct
7 Correct 3 ms 2764 KB Output is correct
8 Correct 2 ms 2772 KB Output is correct
9 Correct 2 ms 2668 KB Output is correct
10 Correct 2 ms 2644 KB Output is correct
11 Correct 2 ms 2672 KB Output is correct
12 Correct 90 ms 13140 KB Output is correct
13 Correct 66 ms 19824 KB Output is correct
14 Correct 45 ms 7572 KB Output is correct
15 Correct 76 ms 7424 KB Output is correct
16 Correct 70 ms 7424 KB Output is correct

Subtask #6
0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 1 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
6 Correct 2 ms 2644 KB Output is correct
7 Correct 3 ms 2764 KB Output is correct
8 Correct 2 ms 2772 KB Output is correct
9 Correct 2 ms 2668 KB Output is correct
10 Correct 2 ms 2644 KB Output is correct
11 Correct 2 ms 2672 KB Output is correct
12 Correct 2 ms 2644 KB Output is correct
13 Incorrect 2 ms 2672 KB Output isn't correct
14 Halted 0 ms 0 KB -

Subtask #7
0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 1 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
6 Correct 2 ms 2644 KB Output is correct
7 Correct 3 ms 2764 KB Output is correct
8 Correct 2 ms 2772 KB Output is correct
9 Correct 2 ms 2668 KB Output is correct
10 Correct 2 ms 2644 KB Output is correct
11 Correct 2 ms 2672 KB Output is correct
12 Correct 90 ms 13140 KB Output is correct
13 Correct 66 ms 19824 KB Output is correct
14 Correct 45 ms 7572 KB Output is correct
15 Correct 76 ms 7424 KB Output is correct
16 Correct 70 ms 7424 KB Output is correct
17 Correct 2 ms 2644 KB Output is correct
18 Incorrect 2 ms 2672 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 2644 KB Output is correct
2 Incorrect 2 ms 2644 KB Output isn't correct
3 Halted 0 ms 0 KB -