求助，54pts，别的点RE

RT

#include <bits/stdc++.h>
typedef long long ll;
using namespace std;
const ll MAXN = 1e5 + 10;
int n, m;
struct node {
    ll l, r;
    ll data;
    ll lmax, rmax, tmax;
} tree[MAXN << 2];
ll a[MAXN];
void update(ll p) {
    tree[p].data = tree[p << 1].data + tree[p << 1 | 1].data;
    tree[p].lmax = max(tree[p << 1].lmax, tree[p << 1].data + tree[p << 1 | 1].lmax);
    tree[p].rmax = max(tree[p << 1 | 1].rmax, tree[p << 1 | 1].data + tree[p << 1].rmax);
    tree[p].tmax = max(max(tree[p << 1].tmax, tree[p << 1 | 1].tmax), tree[p << 1].rmax + tree[p << 1 | 1].lmax);
}
void build(ll p, ll l, ll r) {
    tree[p].l = l;
    tree[p].r = r;
    if (l == r) {
        tree[p].data = tree[p].lmax = tree[p].rmax = tree[p].tmax = a[l];
        return;
    }
    ll mid = (l + r) >> 1;
    build(p << 1, l, mid);
    build(p << 1 | 1, mid + 1, r);
    update(p);
}
node query(ll p, ll l, ll r) {
    if (tree[p].l >= l && tree[p].r <= r) {
        return tree[p];
    }
    node lnode, rnode, tnode;
    tnode.data = 0;
    if (tree[p << 1].r >= l && tree[p << 1 | 1].l <= r) {
        lnode = query(p << 1, l, r);
        rnode = query(p << 1 | 1, l, r);
        tnode.data = lnode.data + rnode.data;
        tnode.lmax = max(lnode.lmax, lnode.data + rnode.lmax);
        tnode.rmax = max(rnode.rmax, rnode.data + lnode.rmax);
        tnode.tmax = max(max(lnode.tmax, rnode.tmax), lnode.rmax + rnode.lmax);
    }
    else if (tree[p << 1].r >= l) tnode = query(p << 1, l, r);
    else if (tree[p << 1 | 1].l <= r) tnode = query(p << 1 | 1, l, r);
    return tnode;
}
void modify(ll p, ll l, ll r, ll val) {
    if (tree[p].l == tree[p].r) {
        tree[p].data = tree[p].lmax = tree[p].rmax = tree[p].tmax = val;
        return;
    }
    if (tree[p << 1].r >= l) modify(p << 1, l, r, val);
    if (tree[p << 1 | 1].l <= r) modify(p << 1 | 1, l, r, val);
    update(p);
}
int main() {
    cin >> n >> m;
    for (ll i = 1; i <= n; i ++) cin >> a[i];
    build(1, 1, n);
    while (m --) {
        int opt, x, y;
        cin >> opt >> x >> y;
        if (opt == 1) {
            if (x > y) swap(x, y);
            cout << query(1, x, y).tmax << endl;
        }
        else modify(1, x, x, y);
    }
    return 0;
}