Submission #1135179

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Source Code Expand

#include<cstdio>
#include<algorithm>
#include<cstring>
#include<iostream>
#include<vector>
#include<set>
#include<map>
#include<bitset>
#include<cmath>
#include<string>

#define ls (t<<1)
#define rs ((t<<1)+1)
#define mid ((l+r)>>1)
#define fi first
#define se second
#define mk make_pair
#define pb push_back

#define N 1005
#define M 200005
#define seed 23333
#define Mo 1000000007

using namespace std;
int i,j,m,n,p,k,f[N][N*2],dis[N],fa[N],Q[N],x,y,dia[N],ans,D,col[N],Dis[N],lim[N];
vector<int>v[N];
void jia(int &x,int y)
{
		x+=y; if (x>=Mo) x-=Mo;
}
void jian(int &x,int y)
{
		x-=y; if (x<0) x+=Mo;
}
int bfs(int *dis,int x)
{
		memset(fa,0,sizeof(fa));
		for (i=1;i<=n;++i) dis[i]=-1;
		dis[x]=0; Q[Q[0]=1]=x;
		int i,l;
		for (l=1;l<=Q[0];++l)
		{
				int p=Q[l];
				for (i=0;i<(int)v[p].size();++i)
				{
						int k=v[p][i];
						if (dis[k]!=-1) continue;
						dis[k]=dis[p]+1;
						fa[k]=p;
						Q[++Q[0]]=k;
				}
		}
		int now=1;
		for (i=1;i<=n;++i) if (dis[now]<dis[i]) now=i;
		return now;
}
void dfs(int x)
{
	  int i,j;
	  for (i=-n+N;i<=n+N;++i) if (abs(i-N)<=D/2-dis[x]) f[x][i]=1; 
	  for (i=0;i<(int)v[x].size();++i)
	  {
	  		int p=v[x][i];
	  		if (fa[x]==p) continue;
	  		dfs(p);
	  		for (j=-n+N;j<=n+N;++j) 
				f[x][j]=1ll*f[x][j]*(f[p][j-1]+f[p][j+1])%Mo;
	  }
}
void Dfs(int x,int tp)
{
	  int i,j;
	  for (i=-n+N;i<=n+N;++i) 
	  	if (col[x])
	  {
	  		if (abs(i-N)<=lim[x]) f[x][i]=1;
	  }
	  else if (abs(i-N-tp)<=lim[x]) f[x][i]=1;
	  for (i=0;i<(int)v[x].size();++i)
	  {
	  		int p=v[x][i];
	  		if (fa[x]==p) continue;
	  		Dfs(p,tp);
	  		for (j=-n+N;j<=n+N;++j) 
				f[x][j]=1ll*f[x][j]*(f[p][j-1]+f[p][j+1])%Mo;
	  }
}
int main()
{
		scanf("%d",&n);
		for (i=1;i<n;++i)
		{
				scanf("%d%d",&x,&y);
				v[x].pb(y); v[y].pb(x); 
		}
		int x=bfs(dis,1),y=bfs(dis,x);
		for (;y;y=fa[y]) dia[++dia[0]]=y;
		if (dia[0]&1)
		{
			 D=dia[0]-1;
			 bfs(dis,dia[D/2+1]);
			 dfs(dia[D/2+1]);
			 for (i=-n+N;i<=n+N;++i) jia(ans,f[dia[D/2+1]][i]);
			 printf("%d\n",ans); 
		}
		else
		{
			D=dia[0]-1;
			bfs(Dis,dia[D/2+2]);
			bfs(dis,dia[D/2+1]);
			for (i=1;i<=n;++i) if (dis[i]<Dis[i]) col[i]=1; 
			for (i=1;i<=n;++i)
				if (col[i]) lim[i]=D/2+1-dis[i];
				else lim[i]=D/2-Dis[i];
			Dfs(dia[D/2+1],0);
			for (i=-n+N;i<=n+N;++i) jia(ans,f[dia[D/2+1]][i]);
			for (i=1;i<=n;++i) 
				if (col[i]) lim[i]=D/2-dis[i];
				else lim[i]=D/2+1-Dis[i];
			memset(f,0,sizeof(f));
			Dfs(dia[D/2+1],0);
			for (i=-n+N;i<=n+N;++i) jia(ans,f[dia[D/2+1]][i]);
			memset(f,0,sizeof(f));
			Dfs(dia[D/2+1],-1);
			for (i=-n+N;i<=n+N;++i) jian(ans,f[dia[D/2+1]][i]);
			memset(f,0,sizeof(f));
			Dfs(dia[D/2+1],1);
			for (i=-n+N;i<=n+N;++i) jian(ans,f[dia[D/2+1]][i]);
			printf("%d\n",ans); 
		}
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:91:17: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d",&n);
                 ^
./Main.cpp:94:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d",&x,&y);
                        ^

Judge Result