【线段树维护复杂状态】Ryuji doesn't want to study

https://nanti.jisuanke.com/t/31460

tree[rt].ans = tree[rt << 1].ans + tree[rt << 1 | 1].ans + tree[rt << 1].sum * tree[rt << 1 | 1].len;

注意询问时的合并操作

代码：

#include 
#include 
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
const int maxn = (int)1e5 + 5;
typedef long long ll;
using namespace std;
int n, q;
ll arr[maxn];
struct Tree {
    ll sum, ans, len;
} tree[maxn << 2];
void pushup(int rt) {
    tree[rt].sum = tree[rt << 1].sum + tree[rt << 1 | 1].sum;
    tree[rt].ans = tree[rt << 1].ans + tree[rt << 1 | 1].ans + tree[rt << 1].sum * tree[rt << 1 | 1].len;
}
void build(int l, int r, int rt) {
    tree[rt].len = r - l + 1;
    if (l == r) {
        tree[rt].sum = tree[rt].ans = arr[l];
        return;
    }
    int m = (l + r) >> 1;
    build(lson);
    build(rson);
    pushup(rt);
}
void update(int p, ll val, int l, int r, int rt) {
    if (l == r) {
        tree[rt].ans = tree[rt].sum = val;
        return;
    }
    int m = (l + r) >> 1;
    if (p <= m) {
        update(p, val, lson);
    }
    else {
        update(p, val, rson);
    }
    pushup(rt);
}
ll _query(int L, int R, int l, int r, int rt) {
    if (L <= l && R >= r) {
        return tree[rt].sum;
    }
    int m = (l + r) >> 1;
    ll res = 0;
    if (L <= m) {
        res += _query(L, R, lson);
    }
    if (R > m) {
        res += _query(L, R, rson);
    }
    return res;
}
ll query(int L, int R, int l, int r, int rt) {
    if (L <= l && R >= r) {
        return tree[rt].ans;
    }
    int m = (l + r) >> 1;
    if (L <= m && R > m) {
        return query(L, m, lson) + query(m + 1, R, rson) + _query(L, m, lson) * (R - m);
    }
    else if (L <= m) {
        return query(L, R, lson);
    }
    else {
        return query(L, R, rson);
    }
}
int main() {
    scanf("%d%d", &n, &q);
    for (int i = 1; i <= n; i++) {
        scanf("%lld", &arr[i]);
    }
    build(1, n, 1);
    while (q--) {
        int op, a, b;
        scanf("%d%d%d", &op, &a, &b);
        if (op == 1) {
            printf("%lld\n", query(a, b, 1, n, 1));
        }
        else {
            update(a, b, 1, n, 1);
        }
    }
}