rt,难道我写了个假的分块，感觉跑得比mn还慢。。。

#include <bits/stdc++.h>
using namespace std;
const int N=100005;
int n,m,op,l,r,bl,tot;
int id[N],L[205],R[205];
double a[N],s[205],tag[205],sq[205],k;
inline void update (int l,int r,double k){
	if (id[l]==id[r]){
		for (int i=l;i<=r;++i){
			sq[id[i]]+=k*k+2*k*a[i];
			a[i]+=k;s[id[i]]+=k;
		}
		return ;
	}
	for (int i=l;i<=R[id[l]];++i){
		sq[id[i]]+=k*k+2*k*a[i];
		a[i]+=k;s[id[i]]+=k;
	}
	for (int i=r;i>=L[id[r]];--i){
		sq[id[i]]+=k*k+2*k*a[i];
		a[i]+=k;s[id[i]]+=k;
	} 
	for (int i=id[l]+1;i<id[r];++i){
		tag[i]+=k;
	}
}
inline double query1 (int l,int r){
	double sum=0;
	int len=r-l+1;
	if (id[l]==id[r]){
		for (int i=l;i<=r;++i){
			sum+=a[i]+tag[id[i]];
		}
		return sum*1./(len);
	}
	for (int i=l;i<=R[id[l]];++i){
		sum+=a[i]+tag[id[i]];
	}
	for (int i=r;i>=L[id[r]];--i){
		sum+=a[i]+tag[id[i]];
	} 
	for (int i=id[l]+1;i<id[r];++i){
		sum+=s[i]; 
	}
	return sum*1./len;
}
inline double query2 (int l,int r){
	double ans=0,sum=0;
	int len=r-l+1;
	if (id[l]==id[r]){
		for (int i=l;i<=r;++i){
			ans+=(a[i]+tag[id[i]])*(a[i]+tag[id[i]]);
			sum+=a[i]+tag[id[i]];
		}
		return ans*1./len-(sum*1./len)*(sum*1./len);
	}
	for (int i=l;i<=R[id[l]];++i){
		ans+=(a[i]+tag[id[i]])*(a[i]+tag[id[i]]);
		sum+=a[i]+tag[id[i]];
	} 
	for (int i=r;i>=L[id[r]];--i){
		ans+=(a[i]+tag[id[i]])*(a[i]+tag[id[i]]);
		sum+=a[i]+tag[id[i]];
	}
	for (int i=id[l]+1;i<id[r];++i){
		ans+=(sq[i]+tag[i])*(sq[i]+tag[i]);
		sum+=s[i];
	}
	return ans*1./len-(sum*1./len)*(sum*1./len);
}
signed main(){
//	freopen ("方差.in","r",stdin);
//	freopen ("方差.out","w",stdout);
	scanf ("%d%d",&n,&m);
	bl=(int) (sqrt (n));
	tot=n/bl+(n%bl!=0);
	for (int i=1;i<=n;++i)
		scanf ("%lf",a+i);
	for (int i=1;i<=n;++i)
		id[N]=(i-1)/bl+1;
	for (int i=1;i<=tot;++i){
		L[i]=(i-1)*bl+1;
		R[i]=i*bl;
	}
	R[tot]=n;
	for (int i=1;i<=n;++i){
		s[id[i]]+=a[i];
		sq[id[i]]+=a[i]*a[i];
	}
	for (int i=1;i<=m;++i){
		scanf ("%d%d%d",&op,&l,&r);
		if (op==1){
			scanf ("%lf",&k);
			update (l,r,k);
		}
		if (op==2){
			printf ("%.4lf\n",query1 (l,r));
		}
		if (op==3){
			printf ("%.4lf\n",query2 (l,r));
		}
	}
	return 0;
}