NOIP2017 提高组部分题解

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小凯的疑惑

题目

https://www.luogu.org/problemnew/show/P3951

代码

#include<bits/stdc++.h>
using namespace std;
int main()
{
	//freopen("math.in","r",stdin);
	//freopen("math.out","w",stdout);
	long long a,b;
	cin>>a>>b; 
	long long n=a*b-a-b;
	cout<<n<<endl;
	return 0;
}

奶酪

题目

https://www.luogu.org/problemnew/show/P3958

代码

#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
inline ll read()
{
	ll f=1,num=0;
	char ch=getchar();
	while (ch<'0'||ch>'9') { if (ch=='-') f=-1;ch=getchar(); }
	while (ch>='0'&&ch<='9') num=(num<<1)+(num<<3)+ch-'0',ch=getchar();
	return num*f;
}
const int maxnum=1e3+10;
ll t,n,h,r,tot,x[maxnum],y[maxnum],z[maxnum];
ll head[maxnum],ver[maxnum*maxnum],Next[maxnum*maxnum];
bool flag;
void add(int x,int y)
{
	ver[++tot]=y,Next[tot]=head[x],head[x]=tot;
}
bool v[maxnum];
void dfs(int s)
{
	if (s==n+1)
	{
		flag=1;
		return ;
	}
	for (int i=head[s];i;i=Next[i])
	{
		if (!v[ver[i]])
		v[ver[i]]=1,dfs(ver[i]);
	}
	return ;
}
int main()
{
	t=read();
	while (t--)
	{
		memset(head,0,sizeof(head));
		memset(ver,0,sizeof(ver));
		memset(Next,0,sizeof(Next));
		n=read(),h=read(),r=read();
		for (int i=1;i<=n;i++)
			x[i]=read(),y[i]=read(),z[i]=read();
		for (int i=1;i<=n;i++)
			for (int j=i+1;j<=n;j++)
				if (2*r>=sqrt(1.0*(x[i]-x[j])*(x[i]-x[j])+1.0*(y[i]-y[j])*(y[i]-y[j])
						+1.0*(z[i]-z[j])*(z[i]-z[j])))
					add(i,j),add(j,i);
		for (int i=1;i<=n;i++) 
			if (r>=z[i]) add(0,i),add(i,0);
		for (int i=1;i<=n;i++)
			if (z[i]+r>=h) add(i,n+1),add(n+1,i);
		memset(v,0,sizeof(v));
		v[0]=1,flag=0;
		dfs(0);
		if (flag) cout<<"Yes"<<endl;
		else cout<<"No"<<endl;
	}
	return 0;
}