bzoj1082

题解：

暴搜+二分+剪枝

二分答案，暴力判断是否有解

然后加上剪枝

代码：

#include<bits/stdc++.h>
using namespace std;
const int N=2005;
int rest,c[N],sum[N],s,a[N],n,m,b[N];
int dfs(int x,int y)
{
    if (x<=0)return 1;
    if (rest+sum[x]>s)return 0;
    for (int i=y;i<=n;i++)
     if (c[i]>=b[x])
      {
         c[i]-=b[x];
         if (c[i]<b[1])rest+=c[i];
         if (b[x]==b[x-1]){if (dfs(x-1,i))return 1;}
         else {if (dfs(x-1,1))return 1;}
         if (c[i]<b[1])rest-=c[i];
         c[i]+=b[x];
      }
    return 0; 
}
int pd(int x)
{
    for (int i=1;i<=n;i++)c[i]=a[i];
    rest=0;
    return dfs(x,1);
}
int main()
{
    scanf("%d",&n);
    for (int i=1;i<=n;i++)scanf("%d",&a[i]),s+=a[i];
    scanf("%d",&m);
    for (int i=1;i<=m;i++)scanf("%d",&b[i]);
    sort(a+1,a+n+1);sort(b+1,b+m+1);
    for (int i=1;i<=m;i++)sum[i]=sum[i-1]+b[i];
    while (sum[m]>s)m--;
    int l=0,r=m;
    while (l<r)
     {
         int mid=(l+r)/2;
         if (pd(mid+1))l=mid+1;
         else r=mid;
     }
    printf("%d",l); 
}