[BZOJ1911][Apio2010]特别行动队

来源：互联网发布：二维数组去重js 编辑：程序博客网时间：2024/04/28 09:40

原题地址

斜率优化…

#include <cstdio>#include <queue>using namespace std;typedef long long ll;const ll N=1000010;ll n,a,b,c;ll x[N],s[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%lld%lld%lld",&n,&a,&b,&c);    for(ll i=1;i<=n;i++) scanf("%lld",&x[i]);    for(ll i=1;i<=n;i++) s[i]=s[i-1]+x[i];    for(ll i=1;i<=n;i++){        ll  A=-s[i];        Vec tmp=Vec(((a*s[i-1])<<1),f[i-1]+a*s[i-1]*s[i-1]-b*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*s[i]*s[i]+b*s[i]+c;    }    printf("%lld\n",f[n]);    return 0;}

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