60 lines
1.5 KiB
C++
60 lines
1.5 KiB
C++
#include<cstdio>
|
|
#include<cstring>
|
|
#include<algorithm>
|
|
using namespace std;
|
|
#define Lc (o<<1)
|
|
#define Rc (o<<1|1)
|
|
const int maxn=50005;
|
|
const int maxidx=200005;
|
|
int n,s,p[maxn][2],d[maxn][2],f[maxn][2];
|
|
int a[maxidx<<2],pl,pr,v;
|
|
inline void pushdown(int o) { a[Lc]=max(a[Lc],a[o]); a[Rc]=max(a[Rc],a[o]); }
|
|
void update(int o,int L,int R)
|
|
{
|
|
if(pl<=L&&R<=pr) { a[o]=max(a[o],v); return; }
|
|
pushdown(o);
|
|
int M=(L+R)>>1;
|
|
if(pl<=M)
|
|
update(Lc,L,M);
|
|
if(pr>M)
|
|
update(Rc,M+1,R);
|
|
}
|
|
int query(int o,int L,int R,int p,int v)
|
|
{
|
|
if(L==R) return max(v,a[o]);
|
|
int M=(L+R)>>1;
|
|
if(p<=M) return query(Lc,L,M,p,max(v,a[o]));
|
|
else return query(Rc,M+1,R,p,max(v,a[o]));
|
|
}
|
|
inline void ckmin(int &a,int b) { a=min(a,b); }
|
|
int main()
|
|
{
|
|
#ifdef local
|
|
freopen("pro.in","r",stdin);
|
|
#endif
|
|
memset(f,0x3f,sizeof(f));
|
|
scanf("%d%d",&n,&s);
|
|
for(int i=1;i<=n;i++)
|
|
{
|
|
scanf("%d%d",&p[i][0],&p[i][1]);
|
|
p[i][0]+=100001; p[i][1]+=100001;
|
|
d[i][0]=query(1,1,maxidx-5,p[i][0],0);
|
|
d[i][1]=query(1,1,maxidx-5,p[i][1],0);
|
|
// printf("i=%d %d %d\n",i,d[i][0],d[i][1]);
|
|
v=i; pl=p[i][0]; pr=p[i][1];
|
|
update(1,1,maxidx-5);
|
|
}
|
|
s+=100001;
|
|
f[n][0]=abs(s-p[n][0]); f[n][1]=abs(s-p[n][1]);
|
|
p[0][0]=p[0][1]=100001;
|
|
for(int i=n;i>=1;i--)
|
|
for(int j=0;j<=1;j++)
|
|
{
|
|
// printf("f[%d][%d]=%d\n",i,j,f[i][j]);
|
|
int v=min(f[i][j],f[i][j^1]+abs(p[i][0]-p[i][1])),to=d[i][j];
|
|
f[to][0]=min(f[to][0],v+abs(p[i][j]-p[to][0]));
|
|
f[to][1]=min(f[to][1],v+abs(p[i][j]-p[to][1]));
|
|
}
|
|
printf("%d\n",f[0][0]);
|
|
return 0;
|
|
} |