线段树求调

#include<cstdio>
#include<algorithm>
#include<iostream>
#include<cmath>
#define int long long
using namespace std;
struct node{
	int sum1,sum2,l,r;
	int lazy;
}tr[800005];
int n,m,a[100005];
void pushdown(int p){
	tr[p * 2].sum1 += (tr[p * 2].r - tr[p * 2].l + 1) * tr[p].lazy;
	tr[p * 2 + 1].sum1 += (tr[p * 2 + 1].r - tr[p * 2 + 1].l + 1) * tr[p].lazy;
	tr[p * 2].sum2 += (tr[p * 2].r - tr[p * 2].l + 1) * tr[p].lazy * tr[p].lazy + 2 * tr[p].lazy * tr[p * 2].sum1;
	tr[p * 2 + 1].sum2 += (tr[p * 2 + 1].r - tr[p * 2 + 1].l + 1) * tr[p].lazy * tr[p].lazy + 2 * tr[p].lazy * tr[p * 2 + 1].sum1;
	tr[p * 2].lazy = tr[p].lazy;
	tr[p * 2 + 1].lazy = tr[p].lazy;
	return ;
}
void build(int p,int l,int r){
	tr[p].l = l,tr[p].r = r;
	if(l == r){
		tr[p].sum1 = a[l];
		tr[p].sum2 = a[l] * a[l];
		return ;
	}
	int mid = (tr[p].l + tr[p].r) / 2;
	build(p * 2,l,mid);
	build(p * 2 + 1,mid + 1,r);
	tr[p].sum1 = tr[p * 2].sum1 + tr[p * 2 + 1].sum1;
	tr[p].sum2 = tr[p * 2].sum2 + tr[p * 2 + 1].sum2;
	return ;
}
void add(int p,int l,int r,int k){
	if(l <= tr[p].l && tr[p].r <= r){
		tr[p].lazy += k;
		tr[p].sum1 += (tr[p].r - tr[p].l + 1) * k;
		tr[p].sum2 += (tr[p].r - tr[p].l + 1) * k * k + 2 * k * tr[p].sum1;
		return ;
	}
	pushdown(p);
	int mid = (tr[p].l + tr[p].r) / 2;
	if(l <= mid) add(p * 2,l,r,k);
	if(r > mid) add(p * 2 + 1,l,r,k);
	tr[p].sum1 = tr[p * 2].sum1 + tr[p * 2 + 1].sum1;
	tr[p].sum2 = tr[p * 2].sum2 + tr[p * 2 + 1].sum2;
	return ;
}
int found(int p,int l,int r){
	if(l <= tr[p].l && tr[p].r <= r) return tr[p].sum1;
	pushdown(p);
	int mid = (tr[p].l + tr[p].r) / 2,ans = 0;
	if(l <= mid) found(p * 2,l,r);
	if(r > mid) found(p * 2 + 1,l,r);
	tr[p].sum1 = tr[p * 2].sum1 + tr[p * 2 + 1].sum1;
	tr[p].sum2 = tr[p * 2].sum2 + tr[p * 2 + 1].sum2;
	return ans;
}
int found_(int p,int l,int r){
	if(l <= tr[p].l && tr[p].r <= r) return tr[p].sum2;
	pushdown(p);
	int mid = (tr[p].l + tr[p].r) / 2,ans = 0;
	if(l <= mid) ans += found(p * 2,l,r);
	if(r > mid) ans += found(p * 2 + 1,l,r);
	tr[p].sum1 = tr[p * 2].sum1 + tr[p * 2 + 1].sum1;
	tr[p].sum2 = tr[p * 2].sum2 + tr[p * 2 + 1].sum2;
	return ans;
}
signed main(){
	scanf("%lld%lld",&n,&m);
	for(int i = 1;i <= n;i++) scanf("%lld",&a[i]);
	build(1,1,n);
	int op,x,y,k;
	for(int i = 1;i <= m;i++){
		scanf("%lld%lld%lld",&op,&x,&y);
		if(op == 1){
			scanf("%lld",&k);
			add(1,x,y,k);
		}
		else if(op == 2){
			double f = found(1,x,y) * 1.0 / (y - x + 1);
			printf("%.4f\n",f);
		}
		else if(op == 3){
			double f = found_(1,x,y) + (y - x + 1) * (found(1,x,y) * 1.0 / (y - x + 1))  * (found(1,x,y) * 1.0 / (y - x + 1)) - 2.0 * (found(1,x,y) * 1.0 / (y - x + 1)) * found(1,x,y);
			printf("%.4f\n",f);
		}
	}
	return 0;
}