【BZOJ】【P1096】【ZJOI2007】【仓库建设】【题解】【斜率优化】

传送门:http://www.lydsy.com/JudgeOnline/problem.php?id=1096

我还是只会凸包+三分……

Code:

#include<bits/stdc++.h>using namespace std;typedef long long LL;const int maxn=1e6+5;struct point{LL x,y;point(LL _x=0,LL _y=0):x(_x),y(_y){}LL operator*(point oth)const{return x*oth.y-y*oth.x;}LL operator^(point oth)const{return x*oth.x+y*oth.y;}point operator-(point oth)const{return point(x-oth.x,y-oth.y);}};LL n;LL f[maxn];LL getint(){LL res=0;char c=getchar();while(!isdigit(c))c=getchar();while(isdigit(c))res=res*10+c-'0',c=getchar();return res;}struct CH{point ch[maxn];int m;CH():m(0){}void push_back(point p){while(m>1&&(ch[m-1]-ch[m-2])*(p-ch[m-1])<=0)m--;ch[m++]=p;}LL Qmin(point p){int l=0,r=m-1;while(r-l>2){int mid1=l+(r-l)/3;int mid2=r-(r-l)/3;if((p^ch[mid1])<(p^ch[mid2]))r=mid2;else l=mid1;}LL ans=1LL<<61;for(int i=l;i<=r;i++)ans=min(ans,p^ch[i]);return ans;}}C;LL c[maxn],p[maxn],x[maxn],sump[maxn],sumxp[maxn];int main(){n=getint();for(int i=1;i<=n;i++)x[i]=getint(),p[i]=getint(),c[i]=getint();for(int i=1;i<=n;i++)sumxp[i]=sumxp[i-1]+x[i]*p[i],sump[i]=sump[i-1]+p[i];//n++;C.push_back(point(0,0));f[1]=c[1];C.push_back(point(sump[1],f[1]+sumxp[1]));for(LL i=2;i<=n;i++){f[i]=1LL<<61;f[i]=C.Qmin(point(-x[i],1))+c[i]-sumxp[i-1]+x[i]*sump[i-1];C.push_back(point(sump[i],f[i]+sumxp[i]));}cout<<f[n]<<endl;return 0;}