【bzoj4653】[Noi2016]区间

离散化+线段树

#include<algorithm>
#include<iostream>
#include<cstdlib>
#include<cstring>
#include<cstdio>
#include<cmath>
using namespace std;

typedef long long LL;

#define INF 0x7fffffff
#define N 5000010

int n,m;

struct data
{
    int l,r,k;

}a[N];

bool operator < (data x,data y)
{
    return x.k<y.k;
}

int b[N];
int add[N],sum[N];

int ans=INF,cnt;

inline int getint()
{
    int x=0,f=1;
    char ch=getchar();
    while (ch>'9' || ch<'0')
    {
        if (ch=='-')
            f=-1;
        ch=getchar();
    }
    while (ch>='0' && ch<='9')
    {
        x=x*10+ch-'0';
        ch=getchar();
    }
    return x*f;
}

inline void pushup(int now)
{
    sum[now]=max(sum[now<<1],sum[now<<1|1]);
}

inline void pushdown(int now)
{
    if (add[now])
    {
        sum[now<<1]+=add[now];
        sum[now<<1|1]+=add[now];
        add[now<<1]+=add[now];
        add[now<<1|1]+=add[now];
        add[now]=0;
    }
}

inline void update(int nowl,int nowr,int now,int l,int r,int d)
{
    if (nowl>=l && nowr<=r)
    {
        sum[now]+=d;
        add[now]+=d;
        return ;
    }
    pushdown(now);
    int mid=nowl+nowr>>1;
    if (l<=mid)
        update(nowl,mid,now<<1,l,r,d);
    if (r>mid)
        update(mid+1,nowr,now<<1|1,l,r,d);
    pushup(now);
}

inline int get(int x)
{
    int l=1,r=cnt,mid;
    while (l<r)
    {
        mid=l+r>>1;
        if (b[mid]>=x)
            r=mid;
        else
            l=mid+1;
    }
    return l;
}

int main()
{
    scanf("%d%d",&n,&m);
    for (int i=1;i<=n;i++)
    {
        scanf("%d%d",&a[i].l,&a[i].r);
        a[i].k=a[i].r-a[i].l+1;
        b[++cnt]=a[i].l;
        b[++cnt]=a[i].r;
    }
    sort(a+1,a+n+1);
    sort(b+1,b+cnt+1);
    for (int i=1;i<=n;i++)
        a[i].l=get(a[i].l),a[i].r=get(a[i].r);
    for (int i=1,j=0;j<=n;)
    {
        if (sum[1]>m)
        {
            update(1,cnt,1,a[i].l,a[i].r,-1);
            i++;
        }
        else if (sum[1]<m)
        {
            j++;
            if (j<=n)
                update(1,cnt,1,a[j].l,a[j].r,1);
        }
        else
        {
            ans=min(ans,a[j].k-a[i].k);
            update(1,cnt,1,a[i].l,a[i].r,-1);
            i++;
        }
    }
    printf("%d\n",ans!=INF ? ans : -1);
    return 0;
}