[BZOJ3437]小P的牧场

原题地址

同BZOJ1096…

AC code:

#include <cstdio>
#include <queue>
using namespace std;
typedef long long ll;
const ll N=1000010;
const ll INF=(1<<29)*(1<<29);
ll n;
ll a[N],b[N],s[N],t[N],f[N];

struct Vec{
    ll x,y;

    Vec() {}

    Vec(ll x,ll y):x(x),y(y) {}

    friend Vec operator-(Vec a,Vec b){
        return Vec(a.x-b.x,a.y-b.y);
    }

    friend ll operator*(Vec a,Vec b){
        return a.x*b.y-a.y*b.x;
    }
};
deque<Vec> Q;

int main(){
    scanf("%lld",&n);
    for(ll i=1;i<=n;i++) scanf("%lld",&a[i]);
    for(ll i=1;i<=n;i++) scanf("%lld",&b[i]);
    for(ll i=1;i<=n;i++) s[i]=s[i-1]+b[i];
    for(ll i=1;i<=n;i++) t[i]=t[i-1]+s[i-1];
    for(ll i=1;i<=n;i++){
        ll  A=-i;
        Vec tmp=Vec(s[i-1],f[i-1]-t[i-1]+(i-1)*s[i-1]);
        while(Q.size()>1){
            Vec a,b;
            a=Q.front();Q.pop_front();b=Q.front();
            if((tmp-a)*(a-b)<0){
                Q.push_front(a);
                break;
            }
        }
        Q.push_front(tmp);
        while(Q.size()>1){
            Vec a,b;
            a=Q.back();Q.pop_back();b=Q.back();
            if(A*a.x+a.y<A*b.x+b.y){
                Q.push_back(a);
                f[i]=A*a.x+a.y;
                break;
            }
            f[i]=A*b.x+b.y;
        }
        f[i]+=a[i]+t[i];
    }
    printf("%lld\n",f[n]);

    return 0;
}