bzoj1010: [HNOI2008]玩具装箱toy

这种题自己讲不清楚....比较蒟蒻 还是推荐一篇博客吧 http://hzwer.com/2114.html

#include<cstdio>
#include<cstring>
#include<algorithm>
#define LL long long
using namespace std;
const int M=50007;
int read(){
    int ans=0,f=1,c=getchar();
    while(c<'0'||c>'9'){if(c=='-') f=-1; c=getchar();}
    while(c>='0'&&c<='9'){ans=ans*10+(c-'0'); c=getchar();}
    return ans*f;
}
int n,l;
LL s[M],f[M],c;
int q[M],w[M];
double slop(int j,int k){
    return (f[k]-f[j]+(s[k]+c)*(s[k]+c)-(s[j]+c)*(s[j]+c))/(2.0*(s[k]-s[j]));
}
int main()
{
    n=read(); l=read(); c=l+1;
    for(int i=1;i<=n;i++) w[i]=read(),s[i]=s[i-1]+w[i];
    for(int i=1;i<=n;i++) s[i]+=i;
    int head=1,tail=1; q[tail]=0;
    for(int i=1;i<=n;i++){
        while(head<tail&&slop(q[head],q[head+1])<=s[i]) head++;
        int v=q[head];
        f[i]=f[v]+(s[i]-s[v]-c)*(s[i]-s[v]-c);
        while(head<tail&&slop(q[tail],i)<slop(q[tail-1],q[tail])) tail--;
        q[++tail]=i;
    }
    printf("%lld\n",f[n]);
    return 0;
}