bzoj4358 premu

题目链接

莫队算法

没有用线段树，而是看了showson的并查集%%%

 #include<algorithm>
 #include<iostream>
 #include<cstdlib>
 #include<cstring>
 #include<cstdio>
 #include<string>
 #include<cmath>
 #include<ctime>
 #include<queue>
 #include<stack>
 #include<map>
 #include<set>
 #define rre(i,r,l) for(int i=(r);i>=(l);i--)
 #define re(i,l,r) for(int i=(l);i<=(r);i++)
 #define Clear(a,b) memset(a,b,sizeof(a))
 #define inout(x) printf("%d",(x))
 #define douin(x) scanf("%lf",&x)
 #define strin(x) scanf("%s",(x))
 #define LLin(x) scanf("%lld",&x)
 #define op operator
 #define CSC main
 typedef unsigned long long ULL;
 typedef const int cint;
 typedef long long LL;
 using namespace std;
 void inin(int &ret)
 {
     ret=;int f=;char ch=getchar();
     while(ch<''||ch>''){if(ch=='-')f=;ch=getchar();}
     while(ch>=''&&ch<='')ret*=,ret+=ch-'',ch=getchar();
     ret=f?-ret:ret;
 }
 int n,m,a[],wei[],temp;
 int fa[],s[],bo[],pos[],sta[],top,ANS[];
 struct que
 {
     int l,r,id;
     void in(int i){inin(l),inin(r),id=i;}
     bool op < (const que &rhs)const {return wei[l]==wei[rhs.l]?r<rhs.r:l<rhs.l;}
 }q[];
 int find(int x){return x==fa[x]?x:fa[x]=find(fa[x]);}
 void merge(int x,int y)
 {
     x=find(x),y=find(y);
     if(x==y)return ;
     s[x]+=s[y];
     temp=max(temp,s[x]);
     fa[y]=x;
 }
 void init()
 {
     re(i,,n)fa[i]=i,s[i]=;
     temp=;
 }
 void add(int x)
 {
     bo[x]=;
     s[x]=;
     if(bo[x-])merge(x-,x);
     if(bo[x+])merge(x,x+);
 }
 int main()
 {
     inin(n);inin(m);
     int nn=sqrt(n);
     re(i,,n)inin(a[i]),wei[i]=(i-)/nn+,pos[a[i]]=i;
     re(i,,m)q[i].in(i);
     sort(q+,q+m+);
     int r=;
     re(i,,m)
     {
         if(i==||wei[q[i].l]!=wei[q[i-].l])
         {
             Clear(bo,);Clear(s,);
             init(),top=;
             int head=(q[i].l-)/nn*nn+;
             r=min(head+nn-,n);
             re(j,head,r)sta[++top]=a[j];
             sort(sta+,sta+top+);
         }
         while(r<q[i].r)add(a[++r]);
         int ans=temp,nl=,nr=;
         re(j,,top)
         {
             int c=sta[j];
             if(pos[c]<q[i].l||pos[c]>q[i].r)continue;
             if(c==nr+)nr+=s[find(c+)]+;
             else
             {
                 ans=max(ans,nr-nl+);
                 nl=c-s[find(c-)];
                 nr=c+s[find(c+)];
             }
         }
         ANS[q[i].id]=max(ans,nr-nl+);
     }
     re(i,,m)printf("%d\n",ANS[i]);
      return ;
 }