BZOJ 1010: [HNOI2008]玩具装箱toy(dp+斜率优化)

要写题解好像很长...不想写(不会写..) BZOJ discuss里讲得挺好的...

------------------------------------------------------------------------------

#include<cstdio>#include<cstring>#include<iostream>#include<algorithm> #define Rep(i,l,r) for(int i=l;i<=r;++i) using namespace std; typedef long long ll;const int maxn=50000+5; ll sum[maxn];ll d[maxn];int q[maxn]; #define A(i) (sum[i]+i)#define B(i) (A(i)+1+l)#define X(k,j) (d[k]+B(k)*B(k)-d[j]-B(j)*B(j))#define Y(k,j) (B(k)-B(j)) int main(){// freopen("test.in","r",stdin);// freopen("test.out","w",stdout); int n,l; scanf("%d%d",&n,&l); sum[0]=0; Rep(i,1,n) { int t; scanf("%d",&t); sum[i]=sum[i-1]+t; } int front=0,rear=0; q[0]=d[0]=0; Rep(i,1,n) { while(rear>front && X(q[front+1],q[front])<=Y(q[front+1],q[front])*2*A(i)) ++front; d[i]=d[q[front]]+(A(i)-B(q[front]))*(A(i)-B(q[front])); while(rear>front && X(i,q[rear])*Y(q[rear],q[rear-1])*2<=X(q[rear],q[rear-1])*Y(i,q[rear])*2) --rear; q[++rear]=i; } printf("%lld\n",d
); return 0;}

------------------------------------------------------------------------------