bzoj 2453: 维护队列

#include<bits/stdc++.h>
#define rep(i,k,n) for(int i=k;i<=(n);i++)
using namespace std;
const int maxn=10005;
const int maxc=1000005;
typedef long long ll;
int a[maxn],b[maxn],pre[maxn],c[maxn],pos[maxn],block,n,q,m,last[maxc],vis[200];
void reset(int x){
int l=(x-1)*block+1,r=min(x*block,n);
rep(i,l,r)pre[i]=b[i];
sort(pre+l,pre+r+1);
}
char s[20];
void change(int x,int y){
rep(i,1,n)last[c[i]]=0;
rep(i,1,m)vis[i]=0;
c[x]=y;
rep(i,1,n){int t=b[i];
b[i]=last[c[i]];
if(t!=b[i])vis[pos[i]]=1;
last[c[i]]=i;
}rep(i,1,m)if(vis[i])reset(i);
}
int find(int x,int v){
int l=(x-1)*block+1,r=min(x*block,n);
int ll=l;
while(l<=r){int mid=(l+r)>>1;
if(pre[mid]<v)l=mid+1;
else r=mid-1;
}return l-ll;
}
int ask(int l,int r){
int ans=0;
rep(i,l,pos[l]*block)if(b[i]<l)ans++;
rep(i,(pos[r]-1)*block+1,r)if(b[i]<l)ans++;
rep(i,pos[l]+1,pos[r]-1)ans+=find(i,l);
return ans;
}
int main(){//freopen("in.in","r",stdin);
scanf("%d%d",&n,&q);
block=sqrt(n);
m=n/block+(n%block ? 1 : 0);
rep(i,1,n){scanf("%d",&c[i]);pos[i]=(i-1)/block+1;}
rep(i,1,n){b[i]=last[c[i]];last[c[i]]=i;}
rep(i,1,m)reset(i);
int l,r;
rep(i,1,q){
scanf("%s%d%d%d",s,&l,&r);
if(s[0]=='R')change(l,r);
else printf("%d\n",ask(l,r));
}
}