codeforces＃266 总结

#include <cstdio>
#include <cstring>
#include <algorithm>
#define N 1005
using namespace std;

int f[N];
int n,m,a,b;

int main()
{
	int i,j,k;
	scanf("%d%d%d%d",&n,&m,&a,&b);
	for(i=1;i<=n;i++)
	{
		f[i]=f[i-1]+a;
		for(j=max(0,i-m);j<i;j++)
		{
			f[i]=min(f[i],f[j]+b);
		}
	}	
	printf("%d\n",f[n]);
	return 0;
}

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <iostream>
using namespace std;

long long n,a,b,c,d;

int main()
{
	cin>>n>>a>>b;
	n=n*6ll;
	if(n<=a*b)
	{
		cout<<a*b;
		printf("\n");
		cout<<a<<' '<<b;
		printf("\n");
		return 0;
	}
	else
	{
		c=n/a;
		if(a*c<n)c++;
		d=n/b;
		if(b*d<n)d++;
		if(a*c<=b*d)
		{
			cout<<a*c;
			printf("\n");
			cout<<a<<' '<<c;
			printf("\n");
			return 0;
		}
		else
		{
			cout<<b*d;
			printf("\n");
			cout<<d<<' '<<b;
			printf("\n");
			return 0;
		}
		
	}
	return 0;
}

#include <cstdio>
#include <cstring>
#include <algorithm>
#include <iostream>
#define N 501000
using namespace std;

int n,a[N],ctl[N],ctr[N];
long long sum,suml[N],sumr[N];
long long ans;
int main()
{
	int i,j,k;
	scanf("%d",&n);	
	for(i=1;i<=n;i++)scanf("%d",&a[i]),sum+=a[i];
	if(sum%3)
	{
		printf("0\n");
		return 0;
	}
	sum/=3;
	for(i=1;i<=n;i++)
	{
		suml[i]=suml[i-1]+a[i];
		ctl[i]=ctl[i-1];
		if(suml[i]==sum)ctl[i]++;
	}
	for(i=n;i;i--)
	{
		sumr[i]=sumr[i+1]+a[i];
		ctr[i]=ctr[i+1];
		if(sumr[i]==sum)ctr[i]++;
	}
	
	for(i=1;i<n-1;i++)
	{
		if(suml[i]==sum)ans+=ctr[i+2];
	}
	cout<<ans;
	return 0;
}

#include <cstdio>
#include <algorithm>
#define N 5001000
using namespace std;

struct KSD
{
	int v,len,next;
}e[N],eq[N];
int head[N],headq[N],cnt,cntq,dcount;
int crs[N],ans[N];
bool visit[N];
int n,m;
void add(int u,int v)
{
	e[++cnt].v=v;
	e[cnt].len=dcount;
	e[cnt].next=head[u];
	head[u]=cnt;
}
void addq(int u,int v,int len)
{
	eq[++cntq].v=v;
	eq[cntq].len=len;
	eq[cntq].next=headq[u];
	headq[u]=cntq;
}
int f[N],l[N];
inline int find(int x)
{
	if(f[x]==x)return x;
	int t=f[x];
	f[x]=find(f[x]);
	l[x]=max(l[x],l[t]);
	return f[x];
}
inline void dfs(int x,int p,int ll)
{
	int i;
	visit[x]=1;
	for(i=head[x];i;i=e[i].next)
	{
		dfs(e[i].v,x,e[i].len);
	}
	for(i=headq[x];i;i=eq[i].next)
	{
		if(find(eq[i].v)==x&&l[eq[i].v]<=eq[i].len)
		{
			ans[i]=1;
		}
	}
	f[x]=p;
	l[x]=ll;
}

int main()
{
//	freopen("test.in","r",stdin);
	int i,j,k;
	int a,b,c;
	scanf("%d%d",&n,&m);
	dcount=1;
	for(i=1;i<=m;i++)
	{
		scanf("%d",&a);
		if(a==1)
		{
			scanf("%d%d",&b,&c);
			add(c,b);
		}
		if(a==2)
		{
			scanf("%d",&b);
			crs[dcount++]=b;
		}
		if(a==3)
		{
			scanf("%d%d",&b,&c);
			if(c>=dcount)++cntq;
			else addq(b,crs[c],c);
		}
	}
	for(i=1;i<=n;i++)f[i]=i;
	for(i=1;i<=n;i++)
	{
		if(!visit[i])dfs(i,i,0);
	}
	for(i=1;i<=cntq;i++)
	{
		if(ans[i])puts("YES");
		else puts("NO");
	}
	return 0;
}