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OI-codes/Luogu/P1531/P1531.cpp

85 lines
1.5 KiB
C++

#include <bits/stdc++.h>
using namespace std;
struct node {
int l, r;
int max;
node() {
l = r = 0;
max = -0x3f3f3f3f;
}
node(int _l, int _r) {
l = _l;
r = _r;
max = -0x3f3f3f3f;
}
} tr[200005 << 2];
int n, m, x, y, a[200005];
char op;
void pushup(int u) {
tr[u].max = max(tr[u << 1].max, tr[u << 1 | 1].max);
}
void build(int u, int l, int r) {
tr[u] = node(l, r);
if (l == r) {
tr[u].max = a[l];
return;
}
int mid = l + r >> 1;
build(u << 1, l, mid);
build(u << 1 | 1, mid + 1, r);
pushup(u);
}
void modify(int u, int x, int d) {
if (tr[u].l == x && tr[u].r == x) {
tr[u].max = max(tr[u].max, d);
return;
}
int mid = tr[u].l + tr[u].r >> 1;
if (x <= mid) {
modify(u << 1, x, d);
} else {
modify(u << 1 | 1, x, d);
}
pushup(u);
}
int query(int u, int l, int r) {
if (tr[u].l >= l && tr[u].r <= r) {
return tr[u].max;
}
int mid = tr[u].l + tr[u].r >> 1;
int v = 0;
if (l <= mid) {
v = query(u << 1, l, r);
}
if (r > mid) {
v = max(v, query(u << 1 | 1, l, r));
}
return v;
}
int main() {
cin >> n >> m;
for (int i = 1; i <= n; i++) {
cin >> a[i];
}
build(1, 1, n);
while (m--) {
cin >> op >> x >> y;
if (op == 'U') {
modify(1, x, y);
} else if (op == 'Q') {
cout << query(1, x, y) << endl;
}
}
return 0;
}