[USACO12MAR]花盆Flowerpot

传送门：

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
using namespace std;
#define ll long long
#define re register
#define fi first
#define se second
const int N=1e5+10;
inline void read(int &a)
{
    a=0;
    int d=1;
    char ch;
    while(ch=getchar(),ch>'9'||ch<'0')
        if(ch=='-')
            d=-1;
    a=ch^48;
    while(ch=getchar(),ch>='0'&&ch<='9')
        a=(a<<3)+(a<<1)+(ch^48);
    a*=d;
}
pair <int,int> q[N];
int maxq[N],minq[N];
int ans=0x3fffffff;
int main()
{
    int n,m;
    read(n);
    read(m);
    int h1,h2,t1,t2;
    h1=h2=1;
    t1=t2=1;
    for(re int i=1;i<=n;i++)
    {
        read(q[i].fi);
        read(q[i].se);
    }
    sort(q+1,q+1+n);
    for(int l=1,r=0;l<=n;l++)
    {
        while(h1<t1&&maxq[h1]<l) h1++;
        while(h2<t2&&minq[h2]<l) h2++;
        while(r<n&&q[maxq[h1]].se-q[minq[h2]].se<m)
        {
            r++;
            while(h1<t1&&q[maxq[t1-1]].se<=q[r].se)
                t1--;
            maxq[t1++]=r;
            while(h2<t2&&q[minq[t2-1]].se>=q[r].se)
                t2--;
            minq[t2++]=r;
        }
        if(q[maxq[h1]].se-q[minq[h2]].se>=m)
            ans=min(ans,q[r].fi-q[l].fi);
    }
    printf("%d",ans>=0x3fffffff?-1:ans);
    return 0;
}