I hate it(单点修改，区间查询)

#include<bits/stdc++.h>
using namespace std;
#define maxn 200000

int b[maxn],v[maxn];
int n,m;
inline int lowbit(int x)
{ 
    return x&(-x);
}

void add(int x,int val)
{
	v[x]=val;
	while (x<=n)
	{
		
		b[x]=max(b[x],val);
		x+=lowbit(x);
	}
}

int query(int x,int y)
{
	int ans=v[y];
	
	while (x<y)
	{   
	   for (y-=1;y-lowbit(y)>=x;y-=lowbit(y))
	     ans=max(ans,b[y]);
	     	ans=max(ans,v[y]);
	     
	}
  return ans;
}
int main(){
	
	
	while (~scanf("%d%d",&n,&m))
	{
		memset(b,0,sizeof(b));
		memset(v,0,sizeof(v));
	for (int i=1;i<=n;i++)
	{ int xx;
		scanf("%d",&xx);
		add(i,xx);
	}
	char s[10];int x,y;
	for (int i=1;i<=m;i++)
	{
		scanf("%s%d%d",s,&x,&y);
		if (s[0]=='Q')
		  printf("%d\n",query(x,y));
		else if (s[0]=='U')
	        add(x,y);
	}
	} 
	return 0;
}