【无聊放个模板系列】BZOJ 1597 斜率优化

STL 双向队列DEQUE版本

 #include<cstdio>
 #include<cstdlib>
 #include<cstring>
 #include<iostream>
 #include<algorithm>
 #include<queue>
 #include<cmath>
 using namespace std;
 #define Maxn 50010
 #define LL long long

 struct node
 {
     LL x,y;
 }t[Maxn];

 bool cmp(node x,node y) {return (x.x==y.x)?(x.y<y.y):(x.x<y.x);}

 deque<node > q;
 LL f[Maxn];

 bool check(node x,node y,LL k)
 {
     return (y.y-x.y)<=k*(y.x-x.x);
 }

 bool check2(node x,node y,node z)
 {
     return  (y.y-x.y)*(z.x-y.x)>=(y.x-x.x)*(z.y-y.y);
 }

 int main()
 {
     LL n;
     scanf("%lld",&n);
     for(LL i=;i<=n;i++) scanf("%lld%lld",&t[i].x,&t[i].y);
     sort(t+,t++n,cmp);
     /*LL p=1;
     for(LL i=2;i<=n;i++) if(t[i].x>t[p].x&&t[i].y<t[p].y) t[++p]=t[i];*/

     LL p=;
     for(LL i=;i<=n;i++)
     {
         while(p>&&t[i].y>=t[p].y) p--;
         t[++p]=t[i];
     }

     while(!q.empty()) q.pop_back();
     node ft;ft.x=t[].y,ft.y=;q.push_front(ft);
     for(LL i=;i<=p;i++)
     {
         while(q.size()>)
         {
             node x=q.front();q.pop_front();
             if(!check(x,q.front(),-t[i].x)) {q.push_front(x);break;}
         }
         node tt;
         f[i]=q.front().y+t[i].x*q.front().x;
         tt.x=t[i+].y;tt.y=f[i];
         while(q.size()>)
         {
             node x=q.back();q.pop_back();
             if(!check2(tt,x,q.back())) {q.push_back(x);break;}
         }
         q.push_back(tt);
         // printf("%d\n",f[i]);
     }
     printf("%lld\n",f[p]);
     return ;
 }

手打队列版本

 #include<cstdio>
 #include<cstdlib>
 #include<cstring>
 #include<iostream>
 #include<algorithm>
 #include<queue>
 #include<cmath>
 using namespace std;
 #define Maxn 50010
 #define LL long long

 struct hp
 {
     LL x,y;
 }a[Maxn];

 bool cmp(hp x,hp y) {return (x.x==y.x)?(x.y<y.y):(x.x<y.x);}

 struct node
 {
     LL x,y;
 }t[Maxn];

 LL f[Maxn];

 bool check(int x,int y,int k)
 {
     LL kk=k;
     return kk*(t[x].x-t[y].x)<=t[x].y-t[y].y;
 }

 bool check2(int x,int y,int z)
 {
     return (t[y].x-t[z].x)*(t[x].y-t[y].y)<=(t[x].x-t[y].x)*(t[y].y-t[z].y);
 }

 int main()
 {
     int n;
     scanf("%d",&n);
     for(int i=;i<=n;i++) scanf("%d%d",&a[i].x,&a[i].y);
     sort(a+,a++n,cmp);
     int cnt=;
     for(int i=;i<=n;i++)
     {
         while(cnt>&&a[i].y>=a[cnt].y) cnt--;
         a[++cnt]=a[i];
     }
     int len=,st;
     t[++len].x=a[].y;t[len].y=;st=;
     for(int i=;i<=cnt;i++)
     {
         while(st<len&&check(st,st+,-a[i].x)) st++;
         f[i]=a[i].x*t[st].x+t[st].y;
         t[].x=a[i+].y;t[].y=f[i];
         while(st<len&&check2(len-,len,)) len--;
         t[++len]=t[];
         // printf("%lld\n",f[i]);
     }
     printf("%lld\n",f[cnt]);
     return ;
 }

斜率优化

2016-11-18 08:30:47