【NOIp模拟赛】value

感觉动规这种东西怎么也学不会了.....

分析

贪心+动规

http://blog.csdn.net/chen1352/article/details/52234046

说的已经很好了。

代码

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
const int maxn=5000+5;
inline int read()
{
    int x=0,f=1; char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1; ch=getchar();}
    while(ch>='0'&&ch<='9'){x=x*10+ch-'0'; ch=getchar();}
    return x*f;
}
int n,ans;
int f[maxn][maxn];
struct node
{
    int v,w;
    bool operator < (const node &j) const {
        return w>j.w;
    }
}a[maxn];
int main()
{
    freopen("value.in","r",stdin);
    freopen("value.out","w",stdout);
    n=read();
    for(int i=1;i<=n;i++)
    a[i].v=read(),a[i].w=read();
    sort(a+1,a+n+1);
    //memset(f,-0x3f,sizeof(f));
    //for(int i=1;i<=n;i++) f[i][0]=0;
    for(int i=1;i<=n;i++)
    for(int j=1;j<=i;j++)
    {
        f[i][j]=max(f[i-1][j],f[i-1][j-1]+a[i].v-a[i].w*(j-1));
        ans=max(ans,f[i][j]);
    }
    printf("%d
",ans);
}