USACO 2003 Fall Orange Cow Exhibition /// 负数01背包 oj22829

#include <bits/stdc++.h>
#define INF 0x3f3f3f3f
using namespace std;
int s[105],f[105],dp[1000*100*2+5];
int main()
{
    int n;
    while(~scanf("%d",&n))
    {
        int mid=n*1000;
        int ed=mid*2+5;
        for(int i=0;i<n;i++) 
            scanf("%d%d",&s[i],&f[i]);
        memset(dp, -INF,  sizeof(dp));
        dp[mid]=0;
        for(int i=0;i<n;i++)
        {
            if(s[i]>=0)
            {
                for(int j=ed;j>=s[i];j--)
                    dp[j]=max(dp[j],dp[j-s[i]]+f[i]);
            }
            else
            {
                for(int j=s[i];j-s[i]<ed;j++)
                    dp[j]=max(dp[j],dp[j-s[i]]+f[i]);
            }
        }
        int ans=-ed;
        for(int i=mid;i<ed;i++)
            if(dp[i]>=0) ans=max(ans,i-mid+dp[i]);
        printf("%d\n",ans);
    }

    return 0;
}