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IDProblemSubmitterResultTimeMemoryLanguageFile sizeSubmit timeJudge time
#165637#6858. Play on TreePPP#AC ✓134ms27544kbC++172.7kb2023-09-05 20:20:012023-09-05 20:20:02

Judging History

你现在查看的是最新测评结果

  • [2023-09-05 20:20:02]
  • 评测
  • 测评结果:AC
  • 用时:134ms
  • 内存:27544kb
  • [2023-09-05 20:20:01]
  • 提交

answer

#ifdef DEBUG
#define _GLIBCXX_DEBUG
#endif
//#pragma GCC optimize("O3")
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;

#define X first
#define Y second

const ll mod = 1000000007;

ll pew(ll a, ll b)
{
    ll res = 1;
    while (b>0)
    {
        if (b&1) res = res*a%mod;
        b >>= 1;
        a = a*a%mod;
    }
    return res;
}

ll t[1200000], cnt[1200000], del[1200000], F[1200000];
pair<ll,ll> mn[1200000];

vector<int> a;

void push(int v)
{
    if (F[v]==1)
    {

    }
}

void build(int v, int v2, int tl, int tr)
{
    t[v2] = cnt[v2] = 0;
    del[v] = del[v2] = 0;
    F[v] = F[v2] = 0;
    if (tl==tr)
    {
        mn[v] = {a[tl],tl};
        t[v] = a[tl];
        cnt[v] = 1;
        return;
    }
    int tm = (tl+tr)/2;
    build(v*2,v2*2,tl,tm);
    build(v*2+1,v2*2+1,tm+1,tr);
}

pair<ll,ll> get(int v, int tl, int tr, int l, int r)
{
    if (tl>=l and tr<=r) return mn[v];
}

void solve()
{
    int n;
    cin >> n;
    vector<vector<pair<int,int>>> g(n);
    vector<pair<int,int>> e;
    for (ll i=0;i+1<n;i++)
    {
        int u, v;
        cin >> u >> v;
        u--, v--;
        e.push_back({u,v});
        g[u].push_back({v,i*2});
        g[v].push_back({u,i*2+1});
        e.push_back({v,u});
    }
    int N = n*2-2;
    vector<int> dp(N,-1), d(n), S(n);
    for (int i=0;i<n;i++) d[i] = g[i].size();
    vector<int> q;
    for (int i=0;i<N;i++)
    {
        int u = e[i].X, v = e[i].Y;
        if (d[u]==1)
        {
            dp[i] = 0;
            q.push_back(i);
        }
    }
    vector<int> was(N);
    for (int w=0;w<q.size();w++)
    {
        int p = q[w];
        int u = e[p].X, v = e[p].Y;
        S[v] ^= dp[p]+1;
        was[p] = 1;
        d[v]--;
        if (d[v]==1)
        {
            for (auto x: g[v])
            {
                int p2 = x.Y;
                if (was[p2^1]==0)
                {
                    dp[p2] = S[v];
                    q.push_back(p2);
                }
            }
        }
        if (d[v]==0)
        {
            for (auto x: g[v])
            {
                int p2 = x.Y;
                if (dp[p2]==-1)
                {
                    dp[p2] = S[v]^(dp[p2^1]+1);
                    q.push_back(p2);
                }
            }
        }
    }
    ll A = 0;
    for (int i=0;i<n;i++)
    {
        if (S[i]!=0) A++;
    }
    A = A*pew(n,mod-2)%mod;
    cout << A << "\n";
}

int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
#ifdef DEBUG
    //freopen("input.txt", "r", stdin);
#endif
    int T;
    cin >> T;
    while (T--) solve();
    return 0;
}

Details

Tip: Click on the bar to expand more detailed information

Test #1:

score: 100
Accepted
time: 134ms
memory: 27544kb

input:

3
199999
144802 35753
35753 9646
9646 148183
9646 167003
9646 199831
9646 193968
9646 182279
9646 185547
9646 106896
9646 196577
9646 150627
9646 147736
9646 180949
9646 179482
9646 196999
9646 191636
9646 184859
9646 173080
9646 155500
9646 191682
9646 169619
9646 191285
9646 106525
9646 187324
964...

output:

256641286
960854812
384481201

result:

ok 3 lines