能用 double 的都用了

鬼畜输入数据

1 2 8 -2.7566713364794850E+0000
1 2 8  2.1308819339610636E+0000
1 1 6  1.5912831262685359E+0000
1 1 8 -2.7779214559122920E+0000
1 1 8 -6.5134523715823889E-0001

#include <bits/stdc++.h>
#define lson p << 1
#define rson p << 1 | 1
using namespace std;

const int N = 100005;

struct Seg {
	int l, r;
	double sum = 0, psum = 0, tag = 0;
	#define l(p) t[p].l
	#define r(p) t[p].r
	#define sum(p) t[p].sum
	#define psum(p) t[p].psum
	#define tag(p) t[p].tag
	#define len(p) (r(p) - l(p) + 1.0)
} t[N << 2];

int n, m, op, x, y;
double a[N], k;

void read(int &a, int ch = 0, int f = 1) {
	while (!isdigit(ch = getchar())) if (ch == '-') f = -1;
	for (a = 0; isdigit(ch); ch = getchar()) a = (a << 3) + (a << 1) + (ch ^ 48); a *= f;
}
inline void pushup(int p) {
	sum(p) = sum(lson) + sum(rson);
	psum(p) = psum(lson) + psum(rson);
}
inline void pushdown(int p) {
	if (tag(p) != 0) {
		tag(lson) += tag(p);
		tag(rson) += tag(p);
		psum(lson) += 2.0 * tag(p) * sum(lson) + len(lson) * tag(p) * tag(p);
		psum(rson) += 2.0 * tag(p) * sum(rson) + len(rson) * tag(p) * tag(p);
		sum(lson) += tag(p) * len(lson);
		sum(rson) += tag(p) * len(rson);
		tag(p) = 0;
	}
}
void build(int p, int l, int r) {
	l(p) = l, r(p) = r, tag(p) = 0;
	if (l == r) {
		sum(p) = a[l];
		psum(p) = a[l] * a[l];
		return;
	}
	int mid = l + r >> 1;
	build(lson, l, mid);
	build(rson, mid + 1, r);
	pushup(p);
}
void maketag(int p, int l, int r, double k) {
	if (l <= l(p) && r >= r(p)) {
		tag(p) += k;
		psum(p) += 2.0 * k * sum(p) + len(p) * k * k;
		sum(p) += k * len(p);
		return;
	}
	pushdown(p);
	int mid = l(p) + r(p) >> 1;
	if (l <= mid) maketag(lson, l, r, k);
	if (r > mid) maketag(rson, l, r, k);
	pushup(p);
}
Seg merge(Seg a, Seg b) {
	Seg res;
	res.sum = a.sum + b.sum;
	res.psum = a.psum + b.psum;
	return res;
}
Seg query(int p, int l, int r) {
	if (l <= l(p) && r >= r(p)) return t[p];
	pushdown(p);
	int mid = l(p) + r(p) >> 1;
	if (r <= mid) return query(lson, l, r);
	if (l > mid) return query(rson, l, r);
	return merge(query(lson, l, r), query(rson, l, r));
}
int main() {
	read(n), read(m);
	for (int i = 1; i <= n; i++) {
		cin >> a[i];
	}
	build(1, 1, n);
	while (m--) {
		read(op), read(x), read(y);
		if (op == 1) {
			cin >> k;
			maketag(1, x, y, k);
		} else if (op == 2) {
			Seg res = query(1, x, y);
			printf("%.4lf\n", res.sum / (y - x + 1.0));
		} else {
			Seg res = query(1, x, y);
			printf("%.4lf\n", res.psum / (double)n - (res.sum / (y - x + 1.0)) * (res.sum / (y - x + 1.0)));
		}
	}
	return 0;
}