Submission #970488

#	Time	Username	Problem	Language	Result	Execution time	Memory
970488		thunopro	The Xana coup (BOI21_xanadu)	C++14	10 / 100	34 ms	10076 KiB

xanadu

#include<bits/stdc++.h>
using namespace std ; 
#define maxn 200009
#define ll long long 
#define pb push_back 
#define fi first 
#define se second 
#define left id<<1
#define right id<<1|1 
#define re exit(0); 
#define _lower(x) lower_bound(v.begin(),v.end(),x)-v.begin()+1
const int mod = 1e9+7 ;
const int INF = 1e9 ; 

typedef vector<int> vi ; 
typedef pair<int,int> pii ; 
typedef vector<pii> vii ; 

template < typename T > void chkmin ( T &a , T b ) { if ( a > b ) a = b ; } 
template < typename T > void chkmax ( T &a , T b ) { if ( a < b ) a = b ; } 

void add ( int &a , int b ) 
{
	a += b ; 
	if ( a >= mod ) a -= mod ; 
	if ( a < 0 ) a += mod ; 
}

void rf () 
{
	freopen ("bai1.inp","r",stdin) ;
}

int _pow ( int a , int n ) 
{
	if ( n == 0 ) return 1 ; 
	int res = _pow (a,n/2) ; 
	if ( n % 2 ) return 1ll*res*res%mod*a%mod ; 
	else return 1ll*res*res%mod ; 
}

int n ; 
vi adjList [maxn] ; 
int light [maxn] ; 

void sub1 () 
{
	int res = 0 ; 
	for ( int i = 1 ; i <= n ; i ++ ) 
	{
		if ( light [i] == 1 ) 
		{
			if ( i == n ) 
			{
				cout << "impossible" ; re 
			}
			light [i+1] ^= 1 ; 
			if ( i+2 <= n ) light [i+2] ^= 1 ; 
			res ++ ; 
		}	
	}
	cout << res ; 
}
int main () 
{
	ios_base::sync_with_stdio(0); 
	cin.tie(0);cout.tie(0); 
//	rf () ; 
	cin >> n ; 
	for ( int i = 1 ; i < n ; i ++ ) 
	{ 
		int u , v ; cin >> u >> v ; 
		adjList [u] . pb (v) ; adjList [v] . pb (u) ; 
	}
	for ( int i = 1 ; i <= n ; i ++ ) cin >> light [i] ; 
	sub1 () ; 
}

Compilation message (stderr)

xanadu.cpp: In function 'void rf()':
xanadu.cpp:31:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   31 |  freopen ("bai1.inp","r",stdin) ;
      |  ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 5
• Subtask 2: 0 / 15
• Subtask 3: 10 / 10
• Subtask 4: 0 / 40
• Subtask 5: 0 / 30