제출 #1196193

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
1196193		shadow_sami	Star Trek (CEOI20_startrek)	C++20	0 / 100	5 ms	12176 KiB

startrek

#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;
typedef long long int ll;
typedef vector<ll> vi;
typedef vector<vector<ll>> vvi;
typedef pair<ll,ll> pi;
typedef map<ll,ll> mi;
typedef long double ld;
typedef vector<ld> vd;
typedef vector<vector<ld>> vvd;
typedef pair<ld,ld> pd;
#define ff first
#define ss second
#define srt(a) sort(a.begin(),a.end());
#define fip(k, n) for (ll i = k; i < n; i++)
#define fjp(k, n) for (ll j = k; j < n; j++)
#define fin(k, n) for (ll i = k; i >= n; i--)
#define fjn(k, n) for (ll j = k; j >= n; j--)
#define fp(k, n, m) for (ll k = n; k < m; k++)
#define fn(k, n, m) for (ll k = n; k >= m; k--)
#define ordered_set tree<pi, null_type,less< pi >, rb_tree_tag,tree_order_statistics_node_update>
#define totalOne(n) __builtin_popcount(n)
#define backZero(n) __builtin_ctzll(n)
#define frontZero(n) __builtin_clzll(n)
#define fx(k) for ( auto x : k )
#define test ll t;cin >> t;while (t--)
#define nli "\n"

// ==========================(debug)============================================================================================== //

#ifdef SAMI
	#define debug(x) cerr<<#x;cerr<<" ";_printn(x);cerr<<nli;
	#define debg() cerr<<nli;
#else
	#define debug(x)
	#define debg() 
#endif


void _printn(ll x){ cerr<<x<<" "; }
void _printn(int x){ cerr<<x<<" "; }
void _printn(ld x){ cerr<<x<<" "; }
void _printn(double x){ cerr<<x<<" "; }
void _printn(string x){ cerr<<x<<" "; }
void _printn(char x){ cerr<<x<<" "; }
void _printn(bool x){ cerr<<x<<" "; }
template<class T,class V>void _printn(pair<T,V> vv);
template<class T> void _printn(vector<T> vv);
template<class T> void _printn(set<T> vv);
template<class T,class V> void _printn(map<T,V> vv);
template<class T> void _printn(multiset<T> vv);
template<class T,class V>void _printn(pair<T,V> vv){ cerr<<"( ";_printn(vv.ff);cerr<<",";_printn(vv.ss);cerr<<")";}
template<class T> void _printn(vector<T> vv){ cerr<<"[ "; for(auto xx:vv){ _printn(xx);cerr<<" "; } cerr<<"]"; };
template<class T> void _printn(set<T> vv){ cerr<<"{ "; for(auto xx:vv){ _printn(xx);cerr<<" "; } cerr<<"}"; };
template<class T> void _printn(multiset<T> vv){ cerr<<"{ "; for(auto xx:vv){ _printn(xx);cerr<<" "; } cerr<<"}"; };
template<class T,class V> void _printn(map<T,V> vv){ cerr<<"{ "; for(auto xx:vv){ _printn(xx);cerr<<" "; } cerr<<"}"; };

// ==========================(debug)============================================================================================== //

ll n,m,tp,tp2,res,cnt,sum,tptp,ans;
const ll mx = 5e5+5;
const ll mod = 1e9+7;

// ==========================(MOD)=============================================================================================== //

ll mod_add(ll aa,ll bb){ return ((aa%mod)+(bb%mod))%mod; }
ll mod_minus(ll aa,ll bb){ return (((aa%mod)-(bb%mod))+10*mod)%mod; }
ll mod_mul(ll aa,ll bb){ return ((aa%mod)*(bb%mod))%mod; }
ll mod_power(ll aa,ll bb){ aa%=mod; ll empowered = 1; bb%=mod-1; while(bb > 0){ if(bb & 1) empowered = mod_mul(empowered,aa); bb = bb >> 1; aa = mod_mul(aa,aa); } return empowered; }
ll mod_divi(ll aa,ll bb){ aa=mod_mul(aa,mod_power(bb,mod-2)); return aa; }

// ==========================(MOD)=============================================================================================== //

bool f = false;
ll sr,de;
vi adj[mx];
ll st[mx];
ll to[mx];
ll dp[mx];
ll dp2[mx];
ll dis[mx];
ll v;

void dfs(ll u,ll par){	
	dp[u] = 0;
	fx(adj[u])
		if(x!=par){
			dis[x] = dis[u] + 1;
			dfs(x,u);			
			if(!dp[x])				
				dp[u] = 1;
		}
	return;
}

void dfs3(ll u,ll par){	

	dp2[u] = 0;
	dp[u] = 0;
	fx(adj[u])
		if(!dp[x]){
			dp2[u] = 1;
			dp[u] = 1;
		}

	ll tnc = 0;	
	fx(adj[u])
		if(!dp[x])
			tnc++;		
	// debug(u);
	// fip(1,n+1)
	// 	cerr<<dp[i]<<" ";
	// cerr<<nli;
	fx(adj[u])
		if(x!=par){						
			if(dp[u] && tnc==1 && !dp[x]){				
				dp[u] = 0;
				dfs3(x,u);				
				dp[u] = 1;
			}
			else
				dfs3(x,u);				
		}	
}

void dfs2(ll u,ll par,ll k){		
	if(dp[1]){
		ans += tp;		
	}
	// else{
	if(k!=-1)
		dp[k] ^= 1;
	if(dp[1])
		ans += tp2;
	if(k!=-1)
		dp[k] ^= 1;
	// }		
	ans %= mod;
	debug(u);
	debug(ans);
	ll tnc = 0;	
	fx(adj[u])
		if(x!=par){						
			if(!dp[x])
				tnc++;
		}
	if(k==-1)k = u;
	fx(adj[u])
		if(x!=par){						
			if(dp[u])
				dfs2(x,u,((tnc==1 && !dp[x])?k:x));
			else
				dfs2(x,u,k);
		}
	return;
}

int main(){
    ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
    mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());	
    #ifdef SAMI
        freopen("input1.txt", "r", stdin);
        freopen("output1.txt", "w", stdout);
        freopen("error1.txt", "w", stderr);
    #endif // ONLINE_JUDGE

        cin>>n>>m;        
        fip(0,n-1)cin>>st[i]>>to[i];
        fp(k,0,n-1){
			sr = st[k];
			de = to[k];
			adj[sr].push_back(de);
			adj[de].push_back(sr);			
		} 
		tp = 0;
		tp2 = 0;
		dis[1] = 0;
		dfs(1,-1);
		dfs3(1,-1);
		// fip(1,n+1)
		// 	cout<<dp2[i]<<" ";
		// cout<<nli;
		fip(1,n+1){
			if(dp2[i])tp++;
			else tp2++;
		}
		// fip(1,n+1)
		// 	cout<<dp2[i]<<" ";
		// cout<<nli;
		dfs(1,-1);
		ans = 0;		
		dfs2(1,-1,-1);		        
        cout<<ans<<nli;
        
    cerr << "Time elapsed: " << setprecision(6) << 1000.0 * clock() / CLOCKS_PER_SEC << "ms\n";
    return 0;
}

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