【bzoj1978】 BEIJING2010 取数游戏 game dp优化

#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<cmath>
#include<iostream>
#include<algorithm>
#define maxn 50010

using namespace std;

int f[maxn];
int dp[1000010];
int a[maxn],n,ans,l;

int main()
{
	scanf("%d%d",&n,&l);
	for (int i=1;i<=n;i++) scanf("%d",&a[i]);
	for (int i=1;i<=n;i++)
	{
		f[i]=1;
		for (int j=1;j*j<=a[i];j++)
		  if (a[i]%j==0)
		  {
		  	if (j>=l) f[i]=max(f[i],dp[j]+1);
		  	if (a[i]/j>=l) f[i]=max(f[i],dp[a[i]/j]+1);
		  }
		ans=max(ans,f[i]);
		for (int j=1;j*j<=a[i];j++)
		  if (a[i]%j==0)
		  {
		  	dp[j]=max(dp[j],f[i]);
		  	dp[a[i]/j]=max(dp[a[i]/j],f[i]);
		  }
	}
	printf("%d\n",ans);
	return 0;
}