P3195 [HNOI2008]玩具装箱

Aimee

跳出来重新审视未注意的细节

就是输出整数aaa

[斜率优化解释]（https://www.luogu.com.cn/blog/hhz6830975/p3195-hnoi2008-wan-ju-zhuang-xiang-toy-xie-shuai-you-hua-ru-men-post）

#include<iostream>
#include<cstring>
#include<algorithm>
#include<cstdio>
#define int long long
#define  db double
using namespace std;
db dp[50001];
int n,l;
int q[50001];
int h,t;
db c[50001];
db sum[500001];
db a(int xx){
	return sum[xx]+xx;
}
db b(int xx){
	return a(xx)+l+1;
}
db x(int xx){
	return b(xx);
}
db y(int xx){
	return dp[xx]+b(xx)*b(xx);
}
db k(int xx,int yy){
	return (y(xx)-y(yy))/(x(xx)-x(yy));
}
signed main(){
	scanf("%d%d",&n,&l);
	for(int i=1;i<=n;++i){
		scanf("%lf",&c[i]);
		sum[i]=sum[i-1]+c[i];
	}
	h=t=1;
	for(int i=1;i<=n;++i){
		while(t>h&&k(q[h],q[h+1])<2*a(i)) h++;
		dp[i]=dp[q[h]]+(a(i)-b(q[h]))*(a(i)-b(q[h]));
		while(t>h&&k(q[t-1],q[t])>k(i,q[t-1])) t--;
		q[++t]=i;
	}
	cout<<(long long)dp[n];
	return 0;
}