BZOJ 1096 [ZJOI2007]仓库建设

#include<cstdio>
#define N 1000005
#define ll long long
#define TEMP N-1
using namespace std;
ll f
, pre
, d
, s
, c
, x
, y
;
bool calc(int a, int b, int c)
{
return (x[b]-x[a])*(y[c]-y[a])-(x[c]-x[a])*(y[b]-y[a])>=0;
}
int main()
{
int n;
scanf("%d",&n);
for(int i = 1; i <= n; i++)
{
scanf("%lld%lld%lld",&d[i],&pre[i],&c[i]);
s[i]=s[i-1]+pre[i-1]*(d[i]-d[i-1]);
pre[i]+=pre[i-1];
}
int head=0, tail=0;
x[tail]=0;
y[tail++]=0;
for(int i = 1; i <= n; i++)
{
while(tail-head>1 && y[head]-y[head+1]<1.0*(x[head]-x[head+1])*(-d[i]))head++;
f[i]=-d[i]*x[head]-y[head]+s[i]+c[i];
x[TEMP]=pre[i];
y[TEMP]=-f[i]+s[i]-pre[i]*d[i];
while(tail-head>1 && calc(tail-2,tail-1,TEMP))tail--;
x[tail]=x[TEMP];
y[tail++]=y[TEMP];
}
printf("%lld\n",f
);
return 0;
}