BZOJ4653: [Noi2016]区间

传送门

UOJ上卡掉一个点，COGS上卡掉两个点..弃疗，不改了，反正BZOJ上过啦hhh

先把区间按长度递增排序。然后每次用线段树维护区间最大覆盖次数，用一个指针随便扫扫就行了。

 //NOI 2016 D2T1
 //by Cydiater
 //2016.9.18
 #pragma GCC optimize("O2")
 #include <iostream>
 #include <cstdio>
 #include <cstdlib>
 #include <cstring>
 #include <string>
 #include <algorithm>
 #include <queue>
 #include <map>
 #include <ctime>
 #include <cmath>
 #include <iomanip>
 using namespace std;
 #define ll long long
 #define up(i,j,n)        for(INT i=j;i<=n;i++)
 #define down(i,j,n)        for(INT i=j;i>=n;i--)
 #define FILE "interval"
 #define INT unsigned int
 ;
 const INT oo=0x3f3f3f3f;
 map<INT,INT> lable;
 inline INT read(){
     ,f=;
     ;ch=getchar();}
     +ch-';ch=getchar();}
     return x*f;
 }
 INT num[MAXN],N,M,top=,cnt=,check=,x,y,v,ans=oo;
 struct Query{
     INT st,nd,len;
 }q[MAXN];
 struct Tree{
     INT maxx,delta;
 }t[MAXN<<];
 namespace solution{
     inline bool cmp(Query a,Query b){return a.len<b.len;}
     inline void downit(INT node){
         )return;
         t[node<<].delta+=t[node].delta;t[node<<|].delta+=t[node].delta;
         t[node<<].maxx+=t[node].delta;t[node<<|].maxx+=t[node].delta;
         t[node].delta=;
     }
     inline ].maxx,t[node<<|].maxx);}
     void updata(INT leftt,INT rightt,INT root){
         downit(root);
         if(leftt>y||rightt<x)        return;
         if(leftt>=x&&rightt<=y){
             t[root].maxx+=v;
             t[root].delta+=v;
             return;
         }
         INT mid=(leftt+rightt)>>;
         updata(leftt,mid,root<<);
         updata(mid+,rightt,root<<|);
         reload(root);
     }
     void init(){
         N=read();M=read();
         up(i,,N){
             q[i].st=read();q[i].nd=read();
             num[++top]=q[i].st;num[++top]=q[i].nd;
         }
         sort(num+,num+top+);
         up(i,,top)if(!lable[num[i]])lable[num[i]]=++cnt;
         up(i,,N){
             q[i].len=q[i].nd-q[i].st;
             q[i].st=lable[q[i].st];
             q[i].nd=lable[q[i].nd];
         }
         sort(q+,q+N+,cmp);
     }
     void slove(){
         up(i,,N){
             ].maxx<M&&check<N){
                 check++;
                 x=q[check].st;y=q[check].nd;v=;
                 updata(,cnt,);
             }
             ].maxx>=M)ans=min(ans,q[check].len-q[i].len);
             x=q[i].st;y=q[i].nd;v=-;
             updata(,cnt,);
         }
     }
     void output(){
         if(ans==oo)puts("-1");
         else cout<<ans<<endl;
     }
 }
 int main(){
     //freopen(FILE".in","r",stdin);
     //freopen(FILE".out","w",stdout);
     //freopen("input.in","r",stdin);
     using namespace solution;
     init();
     slove();
     output();
     ;
 }