线段树求区间最值。
pushup操作时就赋予最大值。
查询操作就好搞了。另外，用cin会wa
#include <bits/stdc++.h>
#define fi first
#define se second
#define INF 0x3f3f3f3f
#define ll long long
#define ld long double
#define mem(ar,num) memset(ar,num,sizeof(ar))
#define me(ar) memset(ar,0,sizeof(ar))
#define lowbit(x) (x&(-x))
#define IOS ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define lcm(a,b) ((a)*(b)/(__gcd((a),(b))))
#define Max 200005
#define mod 1000000007
using namespace std;
typedef pair<int, int> pii;
ll n, m, sum[Max << 2], f, a, b;
void pushup(ll rt) {
sum[rt] = max(sum[rt << 1], sum[rt << 1 | 1]);
}
void build(ll l, ll r, ll rt) {
if(l == r) {
scanf("%d", &sum[rt]);
return;
}
ll m = (r + l) >> 1;
build(l, m, rt << 1);
build(m + 1, r, rt << 1 | 1);
pushup(rt);
}
void update(ll L, ll C, ll l, ll r, ll rt) {
if(l == r) {
sum[rt] = C;
return ;
}
ll m = (l + r) >> 1;
if(L <= m)
update(L, C, l, m, rt << 1);
else
update(L, C, m + 1, r, rt << 1 | 1);
pushup(rt);
}
ll query(ll L, ll R, ll l, ll r, ll rt) {
if(L <= l && r <= R) {
return sum[rt];
}
ll m = (r + l) >> 1;
ll ans = -INF;
if(L <= m)
ans = max(ans, query(L, R, l, m, rt << 1));
if(R > m)
ans = max(ans, query(L, R, m + 1, r, rt << 1 | 1));
return ans;
}
int main() {
while(~scanf("%lld%lld", &n, &m)) {
build(1, n, 1);
for(int i = 0; i < m; i++) {
char c[10];
scanf("%s%lld%lld", &c, &a, &b);
if(c[0] == 'U') {
update(a, b, 1, n, 1);
} else
printf("%lld\n", query(a, b, 1, n, 1));
}
}
return 0;
}