9
//线段树 的基础题，单点更新，区间的最大值
#include<bits/stdc++.h>
using namespace std;
const int maxn=200011;
const int inf=999999999;
#define lson (rt<<1),L,M
#define rson (rt<<1|1),M+1,R
#define M ((L+R)>>1)
#define For(i,n) for(int i=0;i<(n);i++)
template<class T>inline T read(T&x)
{
char c;
while((c=getchar())<=32);
bool ok=false;
if(c=='-')ok=true,c=getchar();
for(x=0; c>32; c=getchar())
x=x*10+c-'0';
if(ok)x=-x;
return x;
}
template<class T> inline void read_(T&x,T&y)
{
read(x);
read(y);
}
template<class T> inline void write(T x)
{
if(x<0)putchar('-'),x=-x;
if(x<10)putchar(x+'0');
else write(x/10),putchar(x%10+'0');
}
template<class T>inline void writeln(T x)
{
write(x);
putchar('\n');
}
//-------IO template------
struct node
{
int maxv;
node(){maxv=0;}
}p[maxn<<2];
int n;
void build(int rt,int L,int R,int cnt)
{
if(cnt>=n)return;
if(L==R)
{
read(p[rt].maxv);
return ;
}
build(lson,cnt+1);
build(rson,cnt+1);
p[rt].maxv=max(p[rt<<1].maxv,p[rt<<1|1].maxv);
}
void update(int rt,int L,int R,int i,int v)
{
if(L==R)
{
p[rt].maxv=v;return ;
}
if(i<=M)
update(lson,i,v);
else
update(rson,i,v);
p[rt].maxv=max(p[rt<<1].maxv,p[rt<<1|1].maxv);
}
int query(int rt,int L,int R,int x,int y)
{
// printf("%d %d %d %d %d\n",rt,L,R,x,y);
if(L==x&&y==R)
{
return p[rt].maxv;
}
if(y<=M)
return query(lson,x,y);
else if(x>M)
return query(rson,x,y);
else
return max(query(lson,x,M),query(rson,M+1,y));
}
int main()
{
#ifndef ONLINE_JUDGE
freopen("in.txt","r",stdin);
#endif // ONLINE_JUDGE
int m,i,j,k,t;
while(~scanf("%d%d",&n,&m))
{
build(1,1,n,1);
char op[2];
//cout<<m<<endl;
while(m--)
{
scanf("%s",op);
int x,y;read_(x,y);
// printf("%s %d %d\n",op,x,y);
if(op[0]=='Q')
{
writeln(query(1,1,n,x,y));
}
else if(op[0]=='U')
{
update(1,1,n,x,y);
}
}
}
return 0;
}
原文：http://blog.csdn.net/u013167299/article/details/44833763