Submission #593044

#	Time	Username	Problem	Language	Result	Execution time	Memory
593044		radal	Subtree (INOI20_subtree)	C++17	12 / 100	74 ms	18000 KiB

Main

#include <bits/stdc++.h>
//#pragma GCC target("sse,sse2")
//#pragma GCC optimize("unroll-loops,O3")
#define rep(i,l,r) for (int i = l; i < r; i++)
#define repr(i,r,l) for (int i = r; i >= l; i--)
#define X first
#define Y second
#define all(x) (x).begin() , (x).end()
#define pb push_back
#define endl '\n'
#define debug(x) cerr << #x << " : " << x << endl;
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int,int> pll;
constexpr int N = 1e5+5,mod = 1e9+7,inf = 1e9+10;
inline int mkay(int a,int b){
    if (a+b >= mod) return a+b-mod;
    if (a+b < 0) return a+b+mod;
    return a+b;
}
 
inline int poww(int a,int k){
    if (k < 0) return 0;
    int z = 1;
    while (k){
        if (k&1) z = 1ll*z*a%mod;
        a = 1ll*a*a%mod;
        k >>= 1;
    } 
    return z; 
}
int n,m,h[N],lw[N],dp[N][2][2][2]; // root bega
bool vis[N];
int mark[N];
vector<int> adj[N];
void pre(int v,int p){
    lw[v] = inf;
    vis[v] = 1;
    for (int u : adj[v]){
        if (u == p) continue;
        if (vis[u] && h[u] < h[v]){
            mark[v] = v;
            lw[v] = h[u];
            continue;
        }
        if (vis[u]) continue;
        h[u] = h[v]+1;
        pre(u,v);
        if (lw[u] <= h[v]){
            mark[v] = u;
            lw[v] = lw[u];
        }
    }
}
void dfs(int v){
    vis[v] = 1;
    for (int u : adj[v]) if (!vis[u])
        dfs(u);
    if (lw[v] > n){
        dp[v][1][0][0] = 1;
        dp[v][0][0][0] = 1;
        int t = 0;
        for (int u : adj[v]){
            if (h[u] == h[v]+1){
                t++;
                dp[v][0][0][0] = mkay(dp[v][0][0][0],mkay(dp[u][0][0][0],dp[u][0][0][1]));
                dp[v][1][0][0] = 1ll*dp[v][1][0][0]*mkay(dp[u][1][0][0],dp[u][1][0][1])%mod;
            }
        }
        dp[v][0][0][0] = mkay(dp[v][0][0][0],dp[v][1][0][0]);
        dp[v][1][0][0] = mkay(dp[v][1][0][0],1);
        dp[v][0][0][0] -= t;
        if (dp[v][0][0][0] < 0) dp[v][0][0][0] += mod;
        return;
    }
    if (mark[v] == v){
        int t = 0;
        dp[v][0][0][1] = 1;
        dp[v][1][1][0] = 1;
        dp[v][1][0][1] = 1;
        dp[v][1][1][1] = 1;
        for(int u : adj[v]){
            if (h[u] == h[v]+1){
                t++;
                dp[v][0][0][1] = mkay(dp[v][0][0][1],mkay(dp[u][0][0][0],dp[u][0][0][1]));
                dp[v][1][1][0] = 1ll*dp[v][1][1][0]*mkay(dp[u][0][0][0],dp[u][0][0][1])%mod;
            }
        }
        dp[v][0][1][0] = dp[v][1][1][0];
        dp[v][0][0][1] -= t;
        if (dp[v][0][0][1] < 0) dp[v][0][0][1] += mod;
        dp[v][0][1][1] = dp[v][0][0][1];
        return;
    }
    if(lw[v] < h[v]){
        int t = 0;
        dp[v][1][0][1] = 1;
        dp[v][1][1][1] = 1;
        dp[v][1][0][0] = 1;
        dp[v][1][1][0] = 1;
        for (int u : adj[v]){
            if (h[u] == h[v]+1){
                t++;
                if (u == mark[v]){
                    dp[v][0][0][1] = mkay(dp[v][0][0][1],dp[u][0][1][1]);
                    dp[v][1][0][1] = 1ll*dp[v][1][0][1]*dp[u][1][0][1]%mod;
                    dp[v][0][1][1] = mkay(dp[v][0][1][1],dp[u][0][1][1]);
                    dp[v][1][1][1] = 1ll*dp[v][1][1][1]*dp[u][1][1][1]%mod;
                    dp[v][0][0][0] = mkay(dp[v][0][0][0],dp[u][0][1][0]);
                    dp[v][0][1][0] = mkay(dp[v][0][1][0],dp[u][0][1][0]);
                    dp[v][1][1][0] = 1ll*dp[v][1][1][0]*dp[u][1][1][0]%mod;
                    dp[v][1][0][0] = 1ll*dp[v][1][0][0]*dp[u][0][0][0]%mod;
                }
                else{
                    dp[v][0][0][1] = mkay(dp[v][0][0][1],mkay(dp[u][0][0][0],dp[u][0][0][1]));
                    dp[v][1][0][1] = 1ll*dp[v][1][0][1]*mkay(dp[u][1][0][1],dp[u][1][0][0])%mod;
                    dp[v][0][1][1] = mkay(dp[v][0][1][1],mkay(dp[u][0][0][1],dp[u][0][0][0]));
                    dp[v][1][1][1] = 1ll*dp[v][1][1][1]*mkay(dp[u][1][1][0],dp[u][1][1][1])%mod;
                    dp[v][1][1][0] = 1ll*dp[v][1][1][0]*mkay(dp[u][1][0][1],dp[u][1][0][0])%mod;
                    dp[v][1][0][0] = 1ll*dp[v][1][0][0]*mkay(dp[u][1][0][0],dp[u][1][0][1])%mod;
                }
            }
        }
        dp[v][0][0][1] = mkay(dp[v][0][0][1],-(t-1)+dp[v][1][0][1]);
        dp[v][0][1][1] = mkay(dp[v][0][1][1],-(t-1)+dp[v][1][1][1]);
        dp[v][0][0][0] = mkay(dp[v][0][0][0],dp[v][1][0][0]);
        dp[v][0][1][0] = mkay(dp[v][0][1][0],dp[v][1][1][0]);
        dp[v][1][1][1] = mkay(dp[v][1][1][1],1);
        dp[v][1][0][1] = mkay(1,dp[v][1][0][1]);
        return;
    }
    dp[v][1][0][0] = 1;
    dp[v][1][0][1] = 1;
    int t = 0;
    for (int u : adj[v]){
        if (h[u] == h[v]+1){
            t++;
            if (u == mark[v]){
                dp[v][1][0][0] = 1ll*dp[v][1][0][0]*dp[u][0][0][0]%mod;
                dp[v][1][0][1] = 1ll*dp[v][1][0][1]*dp[u][1][0][1]%mod;
                dp[v][0][0][1] = mkay(dp[v][0][0][1],mkay(dp[u][0][1][1],dp[u][0][1][0]));
            }
            else{
                dp[v][1][0][0] = 1ll*dp[v][1][0][0]*mkay(dp[u][1][0][1],dp[u][1][0][0])%mod;
                dp[v][1][0][1] = 1ll*dp[v][1][0][1]*mkay(dp[u][1][0][1],dp[u][1][0][0])%mod;
                dp[v][0][0][1] = mkay(dp[v][0][0][1],mkay(dp[u][0][0][1],dp[u][0][0][0]));
            }
        }
    }
    dp[v][1][0][1] = mkay(dp[v][1][0][1],1);
    dp[v][0][0][1] = mkay(dp[v][0][0][1],dp[v][1][0][1]-t);
    dp[v][0][0][0] = dp[v][1][0][0];
}
int main(){
    ios :: sync_with_stdio(0); cin.tie(0);
    cin >> n >> m;
    rep(i,0,m){
        int u,v;
        cin >> u >> v;
        adj[u].pb(v);
        adj[v].pb(u);
    }
    pre(1,0);
    memset(vis,0,sizeof vis);
    dfs(1);
    dp[1][0][0][0] = mkay(dp[1][0][0][0],dp[1][0][0][1]-1);
    cout << dp[1][0][0][0];
    return 0;
}

• Subtask 1: 0 / 8
• Subtask 2: 12 / 12
• Subtask 3: 0 / 30
• Subtask 4: 0 / 50