用C++写一段线段树标准格式

我可以为您提供一段标准格式的线段树代码，如下所示：

#include <bits/stdc++.h>
using namespace std;

const int MAXN = 1e5 + 5;

int n, m;
int a[MAXN], sum[MAXN << 2], lazy[MAXN << 2];

void pushup(int rt) {
    sum[rt] = sum[rt << 1] + sum[rt << 1 | 1];
}

void pushdown(int rt, int ln, int rn) {
    if (lazy[rt]) {
        lazy[rt << 1] += lazy[rt];
        lazy[rt << 1 | 1] += lazy[rt];
        sum[rt << 1] += lazy[rt] * ln;
        sum[rt << 1 | 1] += lazy[rt] * rn;
        lazy[rt] = ;
    }
}

void build(int l, int r, int rt) {
    if (l == r) {
        sum[rt] = a[l];
        return;
    }
    int mid = (l + r) >> 1;
    build(l, mid, rt << 1);
    build(mid + 1, r, rt << 1 | 1);
    pushup(rt);
}

void update(int L, int R, int C, int l, int r, int rt) {
    if (L <= l && r <= R) {
        sum[rt] += C * (r - l + 1);
        lazy[rt] += C;
        return;
    }
    int mid = (l + r) >> 1;
    pushdown(rt, mid - l + 1, r - mid);
    if (L <= mid) update(L, R, C, l, mid, rt << 1);
    if (R > mid) update(L, R, C, mid + 1, r, rt << 1 | 1);
    pushup(rt);
}

int query(int L, int R, int l, int r, int rt) {
    if (L <= l && r <= R) {
        return sum[rt];
    }
    int mid = (l + r) >> 1, ans = ;
    pushdown(rt, mid - l + 1, r - mid);
    if (L <= mid) ans += query(L, R, l, mid, rt << 1);
    if (R > mid) ans += query(L, R, mid + 1, r, rt << 1 | 1);
    return ans;
}

int main() {
    cin >> n >> m;
    for (int i = 1; i <= n; i++) {
        cin >> a[i];
    }
    build(1, n, 1);
    while (m--) {
        int op, x, y, k;
        cin >> op;
        if (op == 1) {
            cin >> x >> y >> k;
            update(x, y, k, 1, n, 1);
        } else {
            cin >> x >> y;
            cout << query(x, y, 1, n, 1) << endl;
        }
    }
    return ;
}