CF1083E The Fair Nut and Rectangles

传送门

记麻麻我终于学会斜率优化了TAT

孙神一眼切是个dp然后我就推了发斜率优化竟然对了诶嘿嘿

然后直接斜率优化维护下凸壳就吼了啊qwq

【别忘了先排序= =||】

又是忘了开longlong的一天doge

斜率优化大概是会推了= =+

又一个flag立下了= =+

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
#define inf 20021225
#define ll long long
#define db double
#define eps 1e-7
using namespace std;

struct point{int x,y;ll a;}p[1000100];
bool cmp(point a,point b){return a.x<b.x;}
ll f[1000100];
db slope(int x,int y)//x>y
{
	return ((db)f[x]-f[y])/((db)p[x].x-p[y].x);
}
bool check(int i,int j,int k)//i >j >k
{
	return slope(j,k)>p[i].y;
}
int que[1000100];
int main()
{
	int n;ll ans=0;
	scanf("%d",&n);
	for(int i=1;i<=n;i++)	scanf("%d%d%I64d",&p[i].x,&p[i].y,&p[i].a);
	sort(p+1,p+n+1,cmp);
	int hd=0,tl=0;
	for(int i=1;i<=n;i++)	f[i]=-p[i].a+(ll)p[i].x*p[i].y,ans=max(ans,f[i]);
	que[hd]=1;
	for(int i=2;i<=n;i++)
	{
		while(hd<tl&&check(i,que[hd+1],que[hd]))	hd++;
		int pos=que[hd];
		f[i]=max(f[i],f[pos]-p[i].a+(ll)p[i].y*(p[i].x-p[pos].x));
		ans=max(ans,f[i]);//printf("%d 
",f[pos]-p[i].a+p[i].y*(p[pos].x-p[i].x));
		while(hd<tl&&slope(que[tl],que[tl-1])<slope(i,que[tl]))	tl--;
		que[++tl]=i;
	}
	printf("%I64d
",ans);
	return 0;
}

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