Submission #659561

#	Time	Username	Problem	Language	Result	Execution time	Memory
659561		Lobo	Star Trek (CEOI20_startrek)	C++17	0 / 100	18 ms	35824 KiB

startrek

#include<bits/stdc++.h>
using namespace std;
const long long inf = (long long) 1e18 + 10;
const int inf1 = (int) 1e9 + 10;
#define int long long
#define dbl long double
#define endl '\n'
#define sc second
#define fr first
#define mp make_pair
#define pb push_back
#define all(x) x.begin(), x.end()

const int maxn = 5e5+10;
const int mod = 1e9+7;

int n, d, SL, SW, dpw[maxn][2], dpl[maxn][2];
vector<int> g[maxn];

void dfs1(int u, int ant) {
    dpw[u][1] = SW*dpw[u][0] + SL*(dpw[u][0]+dpl[u][0]); dpw[u][1]%= mod;
    dpl[u][1] = 0;

    int qtl = 0;
    for(auto v : g[u]) if(v != ant) {
        qtl+= dpl[v][0];
        dfs1(v,u);
    }

    for(auto v : g[u]) if(v != ant) {
        qtl-= dpl[v][0];
        if(qtl) {
            dpw[u][1]+= dpw[v][1]+dpl[v][1]; dpw[u][1]%= mod;
            dpl[u][1]+= 0;
        }
        else {
            dpw[u][1]+= dpl[v][1]; dpw[u][1]%= mod;
            dpl[u][1]+= dpw[v][1]; dpl[u][1]%= mod;
        }
        qtl+= dpl[v][0];
    }
}

map<int,int> wp[maxn];
int solwp(int u, int ant) {
    if(wp[u].count(ant)) return wp[u][ant];
    wp[u][ant] = 0;
    for(auto v : g[u]) if(v != ant) {
        if(solwp(v,u) == 0) wp[u][ant] = 1;
    }
    return wp[u][ant];
}

void dfs0(int u, int ant) {
    dpw[u][0] = 0;
    for(auto v : g[u]) if(v != ant) {
        dfs0(v,u);
    }
    for(auto v : g[u]) if(v != ant) {
        if(solwp(v,u) == 0) dpw[u][0] = 1;
    }
    dpl[u][0] = 1-dpw[u][0];
}

void solve() {
    cin >> n >> d;

    for(int i = 1; i <= n-1; i++) {
        int u,v; cin >> u >> v;
        int idu = g[u].size();
        int idv = g[v].size();
        g[u].pb(v);
        g[v].pb(u);
    }
    for(int i = 1; i <= n; i++) {
        if(solwp(i,0) == 1) SW++;
        else SL++;
    }

    dfs0(1,0);
    dfs1(1,0);

    cout << dpw[1][1] << endl;

}

int32_t main() {
    ios::sync_with_stdio(false); cin.tie(0);

    // freopen("in.in", "r", stdin);
    // freopen("out.out", "w", stdout);
    int tt = 1;
    // cin >> tt;
    while(tt--) {
        solve();
    }

}

Compilation message (stderr)

startrek.cpp: In function 'void solve()':
startrek.cpp:70:13: warning: unused variable 'idu' [-Wunused-variable]
   70 |         int idu = g[u].size();
      |             ^~~
startrek.cpp:71:13: warning: unused variable 'idv' [-Wunused-variable]
   71 |         int idv = g[v].size();
      |             ^~~

• Subtask 1: 0 / 0
• Subtask 2: 0 / 7
• Subtask 3: 0 / 8
• Subtask 4: 0 / 15
• Subtask 5: 0 / 15
• Subtask 6: 0 / 20
• Subtask 7: 0 / 20
• Subtask 8: 0 / 15