bzoj1049: [HAOI2006]数字序列

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define ll long long
using namespace std;
int read()
{
char ch=getchar();int f=0,x=1;
while(ch<'0'||ch>'9'){if(ch=='-') x=-1;ch=getchar();}
while(ch>='0'&&ch<='9'){f=(f<<1)+(f<<3)+ch-'0';ch=getchar();}
return f*x;
}
int n;
struct node
{
int from;
int to;
int next;
}edge[50005];
int head[50005],a[50005],aa[50005];
int f[50005],mn[50005],tot,L;
long long g[50005],s1[50005],s2[50005];
void add(int u,int v)
{
edge[tot].from=u;
edge[tot].to=v;
edge[tot].next=head[u];
head[u]=tot++;
}
void solve()
{
for(int i=n;i>=0;i--)
{
add(f[i],i);
g[i]=1LL<<60;
}
g[0]=0;a[0]=-(1<<30);
for(int x=1;x<=n;x++)
{
for(int i=head[f[x]-1];i!=-1;i=edge[i].next)
{
if(edge[i].to>x) break;
if(a[edge[i].to]>a[x]) continue;
for(int j=edge[i].to;j<=x;j++)
s1[j]=abs(a[edge[i].to]-a[j]),s2[j]=abs(a[x]-a[j]);
for(int j=edge[i].to+1;j<=x;j++)
s1[j]+=s1[j-1],s2[j]+=s2[j-1];
for(int j=edge[i].to;j<x;j++)
{
g[x]=min(g[x],g[edge[i].to]+s1[j]-s1[edge[i].to]+s2[x]-s2[j]);
}
}
}
}
int find(int x)
{
int l=1,r=L,t=0;
while(l<=r)
{
int mid=(l+r)>>1;
if(mn[mid]<=x)t=mid,l=mid+1;
else r=mid-1;
}
return t;
}
int main()
{
memset(head,-1,sizeof(head));
n=read();
for(int i=1;i<=n;i++)
{
aa[i]=read();
a[i]=aa[i]-i;
}
a[++n] =(1<<30);
memset(mn,127,sizeof(mn));
mn[0]=-(1<<30);
for(int i=1;i<=n;i++)
{
int t=find(a[i]);
f[i]=t+1;
L=max(L,t+1);
mn[t+1]=min(mn[t+1],a[i]);
}
printf("%d\n",n-f
);
solve();
printf("%lld",g
);
}