B - I Hate It

/*线段树求最值*/
#include"iostream"
#include"cstring"
#include"cstdio"
#include"algorithm"  //include"swap,max" 
using namespace std;
//#define lson rt<<1,l,mid define 好耗时间，
//#define rson rt<<1|1,mid+1,r
//#define max(a,b)  ((a)>(b))?(a):(b)
#define MAX 200009
int stu[MAX];
struct node
{
    int l;
    int r;
    int maxn;

}tree[4*MAX];
void build(int rt,int l,int r)
{
    tree[rt].l=l;
    tree[rt].r=r;
    int mid=(l+r)>>1;
    if(l==r)
    {
        tree[rt].maxn=stu[mid];
        return ;
    }
    build(rt<<1,l,mid);
    build(rt<<1|1,mid+1,r);
    tree[rt].maxn=max(tree[rt<<1].maxn,tree[rt<<1|1].maxn);
}
int query(int rt,int x,int y)
{
    int l=tree[rt].l;
    int r=tree[rt].r;
    if(l==x&&r==y)
       return tree[rt].maxn;
    int mid=(l+r)>>1;
    if(x<=mid&&y<=mid)
       return query(rt<<1,x,y);
    else if(x>mid)
       return query(rt<<1|1,x,y);
    else
       return max(query(rt<<1,x,mid),query(rt<<1|1,mid+1,y));             
}
void updata(int rt,int x,int d)
{
    int l,r,mid;
    l=tree[rt].l;
    r=tree[rt].r;
    mid=(l+r)>>1;
    if(l==r)
    {
        tree[rt].maxn=d;
        return ;
    }
    if(x<=mid)
       updata(rt<<1,x,d);
    else
       updata(rt<<1|1,x,d);
    tree[rt].maxn=max(query(rt<<1,l,mid),query(rt<<1|1,mid+1,r));      
}
int main()
{
    int n,m;
    int a,b,i;
    char c;
    while(scanf("%d%d",&n,&m)!=EOF)
    {
        for(i=1;i<=n;i++)
           scanf("%d",&stu[i]);
        build(1,1,n);
        for(i=1;i<=m;i++)
        {
            getchar();//整数后是字符 
            scanf("%c%d%d",&c,&a,&b);
            if(c==‘Q‘)
            {
                printf("%d\n",query(1,a,b));
            }
            else if(c==‘U‘)
               updata(1,a,b);
        }  
    } 
    return 0;
}