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| #include <iostream>
using namespace std;
const int N = 5e5 + 10, INF = -5e8 - 10;
int n, m, k, a, b;
struct Node {
int l, r;
int lmax, rmax, sum, tmax;
} tr[N << 2];
void pushup(Node &rt, Node &left, Node &right) {
rt.tmax = max(left.rmax + right.lmax, max(left.tmax, right.tmax));
rt.lmax = max(left.lmax, left.sum + right.lmax);
rt.rmax = max(right.rmax, left.rmax + right.sum);
rt.sum = left.sum + right.sum;
}
void pushup(int u) {
auto &rt = tr[u], &left = tr[u << 1], &right = tr[u << 1 | 1];
pushup(rt, left, right);
}
void build(int u, int l, int r) {
tr[u] = {l, r};
if (l == r) {
scanf("%d", &a);
tr[u].lmax = tr[u].rmax = tr[u].sum = tr[u].tmax = a;
return;
}
int mid = l + r >> 1;
build(u << 1, l, mid), build(u << 1 | 1, mid + 1, r);
pushup(u);
}
Node query(int u, int l, int r) {
if (l <= tr[u].l && tr[u].r <= r) return tr[u];
int mid = tr[u].l + tr[u].r >> 1;
if (r <= mid) return query(u << 1, l, r);
if (l > mid) return query(u << 1 | 1, l, r);
Node ans, ln = query(u << 1, l, r), rn = query(u << 1 | 1, l, r);
pushup(ans, ln, rn);
return ans;
}
void update(int u, int i, int v) {
if (tr[u].l == i && tr[u].r == i) {
tr[u].lmax = tr[u].rmax = tr[u].sum = tr[u].tmax = v;
return;
}
int mid = tr[u].l + tr[u].r >> 1;
if (i <= mid) update(u << 1, i, v);
else update(u << 1 | 1, i, v);
pushup(u);
}
int main() {
scanf("%d%d", &n, &m);
build(1, 1, n);
while (m--) {
scanf("%d%d%d", &k, &a, &b);
if (k == 1) {
if (a > b) swap(a, b);
printf("%d\n", query(1, a, b).tmax);
} else {
update(1, a, b);
}
}
return 0;
}
|