ZOJ1366 Cash Machine 优化的dp

</pre><pre name="code" class="cpp">#include<stdio.h>
#include<string.h>
int f[100001];
int m[11],v[11];
int max(int x,int y)
{
	if(x<y)return y;
	else return x;
}
int main()
{
	freopen("t.txt","r",stdin);
	int cash,n,i,k,j;
	while(~scanf("%d%d",&cash,&n))
	{
		for(i=1;i<=n;i++)
			scanf("%d%d",&m[i],&v[i]);
		if(!cash||!n){printf("0\n");continue;}		
		memset(f,0,sizeof(f));
		for(i=1;i<=n;i++)
			if(m[i]*v[i]>=cash)
				for(j=v[i];j<=cash;j++)
					f[j]=max(f[j],f[j-v[i]]+v[i]);
			else
			{
				int k=1;
				while(k<m[i])
				{
					for(j=cash;j>=k*v[i];j--)
						f[j]=max(f[j],f[j-k*v[i]]+k*v[i]);
					m[i]=m[i]-k;
					k=2*k;					
				}
				for(j=cash;j>=m[i]*v[i];j--)
					f[j]=max(f[j],f[j-m[i]*v[i]]+m[i]*v[i]);
			}
		printf("%d\n",f[cash]);
	}
	return 0;
}