Submission #577777

#	Time	Username	Problem	Language	Result	Execution time	Memory
577777		juggernaut	Star Trek (CEOI20_startrek)	C++14	0 / 100	2 ms	2644 KiB

startrek

#include<bits/stdc++.h>
#define fr first
#define sc second
using namespace std;
typedef long long ll;
typedef long double ld;
#define USING_ORDERED_SET 0
#if USING_ORDERED_SET
#include<bits/extc++.h>
using namespace __gnu_pbds;
template<class T>using ordered_set=tree<T,null_type,less<T>,rb_tree_tag,tree_order_statistics_node_update>;
#endif
template<class T>void umax(T &a,T b){if(a<b)a=b;}
template<class T>void umin(T &a,T b){if(b<a)a=b;}
#ifdef juggernaut
    #define printl(args...) printf(args)
#else
    #define printl(args...) 0
#endif
int n;
ll d;
vector<int>g[100005];
ll dp[100005];
void dfs(int v,int p){
	ll carry=0;
	for(int to:g[v])if(to^p){
		dfs(to,v);
		if(dp[to]<0)dp[v]-=dp[to];
		else carry-=dp[to];
	}
	if(!dp[v])dp[v]=carry;
	if(!dp[v])dp[v]--;
}
ll mod=1e9+7;
ll ans;
ll losers;
void go(int v,int p,bool depth){
	if(depth){
		if(dp[v]>0)ans+=n;
		else ans+=losers;
	}else{
		if(dp[v]<0)ans+=(n-losers);
	}
	for(int to:g[v])if(to^p)go(to,v,depth^1);
}
bool up[100005];
void chk(int v,int p){
	if(p){
		up[v]=true;
		if(up[p]&&dp[p]>0&&dp[p]==-dp[v])up[v]=false;
		if(dp[v]<0&&!up[v])losers++;
	}else{
		if(dp[v]<0)losers++;
		up[v]=false;
	}
	for(int to:g[v])if(to^p)chk(to,v);
}
int main(){
	scanf("%d%lld",&n,&d);
	for(int i=1;i<n;i++){
		int x,y;
		scanf("%d%d",&x,&y);
		g[x].push_back(y);
		g[y].push_back(x);
	}
	dfs(1,0);
	chk(1,0);
	go(1,0,1);
	ans%=mod;
	printf("%lld",ans);
}

Compilation message (stderr)

startrek.cpp: In function 'int main()':
startrek.cpp:59:7: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   59 |  scanf("%d%lld",&n,&d);
      |  ~~~~~^~~~~~~~~~~~~~~~
startrek.cpp:62:8: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   62 |   scanf("%d%d",&x,&y);
      |   ~~~~~^~~~~~~~~~~~~~

• 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