ac代码(注意字符读入前需要注意回车的影响)
#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<bitset>
#include<cassert>
#include<cctype>
#include<cmath>
#include<cstdlib>
#include<ctime>
#include<deque>
#include<iomanip>
#include<list>
#include<map>
#include<queue>
#include<set>
#include<stack>
#include<vector>
#define mp make_pair
#define pi acos(-1)
#define pii pair<int, int>
#define pll pair<long long , long long>
#define ll long long
#define ld long double
#define MEMS(x) memset(x, -1, sizeof(x))
#define MEM(x) memset(x, 0, sizeof(x))
const int inf = 0x3f3f3f3f;
const int maxn = 200005;
using namespace std;
int N, M;
int s, c[maxn], d[maxn];
char order;
int lowbit(int x)
{
return x & (-x);
}
void update(int x)
{
while(x <= N)
{
d[x] = c[x];
int lx = lowbit(x);
for(int i = 1; i < lx; i <<= 1)
d[x] = max(d[x], d[x - i]);
x += lowbit(x);
}
}
int getmax(int l, int r)
{
int ans = 0;
while(r >= l)
{
ans = max(ans, c[r]);
--r;
while(r - lowbit(r) >= l)
{
ans = max(ans, d[r]);
r -= lowbit(r);
}
}
return ans;
}
int main()
{
// freopen("input.txt", "r", stdin);
// freopen("output.txt", "w", stdout);
while(scanf("%d %d", &N, &M) != EOF)
{
memset(d, 0, sizeof(d));
for(int i = 1; i <= N; i++)
{
scanf("%d", &c[i]);
update(i);
}
int a, b;
while(M--)
{
getchar();
scanf("%c %d %d", &order, &a, &b);
if(order == 'U')
{
c[a] = b;
update(a);
}
else if(order == 'Q')
printf("%d\n", getmax(a, b));
}
}
}