分块算法板子

#include<stdio.h>
#include<math.h>
#include<algorithm>
#define FOR(i,s,t) for(register int i=s;i<=t;++i)
using std::sort;
using std::lower_bound;
const int N=10011;
const int M=1000011;
inline int min(int a,int b){
	return a<b?a:b;
}
int n,q,m,blo;
int c[N],pos[N],pre[N],b[N],last[M];
inline int find(int x,int v){
	int l=(x-1)*blo+1,r=min(x*blo,n);
	return lower_bound(pre+l,pre+r+1,v)-pre-l;
}
inline void reset(int x){
	int l=(x-1)*blo+1,r=min(x*blo,n);
	FOR(i,l,r)pre[i]=b[i];
	sort(pre+l,pre+r+1);
}
inline void build(){
	FOR(i,1,n){
		b[i]=last[c[i]];
		last[c[i]]=i;
		pos[i]=(i-1)/blo+1;
	}
	FOR(i,1,m)reset(i);
}
inline int ask(int l,int r){
	int ans=0;
	if(pos[l]==pos[r]){
		FOR(i,l,r)if(b[i]<l)++ans;
		return ans;
	}
	for(register int i=l;i<=blo*pos[l];++i)if(b[i]<l)++ans;
	for(register int i=blo*(pos[r]-1)+1;i<=r;++i)if(b[i]<l)++ans;
	for(register int i=pos[l]+1;i<pos[r];++i)ans+=find(i,l);
	return ans;
}
inline void change(int x,int v){
	FOR(i,1,n)last[c[i]]=0;
	c[x]=v;
	FOR(i,1,n){
		int t=b[i];
		b[i]=last[c[i]];
		if(t!=b[i])reset(pos[i]);
		last[c[i]]=i;
	}
}
int main(){
	scanf("%d%d",&n,&q);
	FOR(i,1,n)scanf("%d",c+i);
	blo=int(sqrt(n));
	m=n%blo?(n/blo+1):n/blo;
	build();
	char ch[5];int x,y;
	while(q--){
		scanf("%s%d%d",ch,&x,&y);
		if(ch[0]==‘Q‘)printf("%d\n",ask(x,y));
		else change(x,y);
	}
	return 0;
}