OJ-Problems-Source/HDOJ/4258_autoAC.cpp

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#include <cstdio>
#include <iostream>
#include <fstream>
#include <cstring>
using namespace std;
int N,C;
long long a[1000010];
long long f[1000010];
struct point
{
int id;
long long x,y;
point(int a,long long b,long long c)
{
id = a;x = b;y = c;
}
point(){};
};
long long solve()
{
static point s[1000010];
int head = 1,tail = 0;
long long temp;
for (int i = 1;i <= N;i++)
{
point p(i-1,a[i],f[i-1]+ a[i]*a[i]);
while(tail-1 >= head && (s[tail].x - s[tail-1].x)*(p.y - s[tail].y) - (s[tail].y - s[tail-1].y) *(p.x - s[tail].x) <0)
tail --;
s[++tail] = p;
while (head <= tail && (temp = s[head].y - 2*a[i]*s[head].x+a[i]*a[i] + C,temp < f[i]||f[i] == -1))
{
f[i] = temp;
head++;
}
head--;
}
return f[N];
}
int main()
{
while(scanf("%d%d",&N,&C),N+C)
{
a[0] = 0;
for(int i = 1;i <= N;i++)
scanf("%d",&a[i]);
memset(f,-1,sizeof(f));
f[0] = 0;
printf("%I64d\n",solve());
}
return 0;
}