hdu 1754 I Hate It

位运算的时候注意括号。。。一定是我写的太不科学了，和没用位运算比起来没快多少。。。

#include<cstdio>
#include<iostream>
#include<algorithm>
using namespace std;
const int maxn=200010;
int a[maxn];
char test[10];
int tree[maxn*4];
void build(int node,int left,int right)
{
    int mid=(left+right)>>1;
    if(left==right)
    {
        tree[node]=a[mid];
    }
    else
    {
        build((node<<1),left,mid);
        build((node<<1)+1,mid+1,right);
        tree[node]=max(tree[(node<<1)],tree[(node<<1)+1]);
    }
}
void change(int node,int left,int right,int x,int v)
{
    int mid=(left+right)>>1;
    if(left==x&&right==x)
    {
        tree[node]=v;
        return ;
    }
    if(x<=mid)
    {
        change((node<<1),left,mid,x,v);
    }
    else if(x>mid)
    {
        change((node<<1)+1,mid+1,right,x,v);
    }
    tree[node]=max(tree[(node<<1)],tree[(node<<1)+1]);
}
int query(int node,int left,int right,int x,int y)
{
    if(x<=left&&right<=y)
    {
        return tree[node];
    }
    else
    {
        int mid=(left+right)>>1;
        if(x>mid)
        {
            return query((node<<1)+1,mid+1,right,x,y);
        }
        else if(y<=mid)
        {
            return query((node<<1),left,mid,x,y);
        }
        else
        {
            return max(query((node<<1),left,mid,x,y),query((node<<1)+1,mid+1,right,x,y));
        }
    }
}
int main()
{
    int n,m;
    while(scanf("%d%d",&n,&m)==2)
    {
        for(int i=1;i<=n;i++)
        {
            scanf("%d",&a[i]);
        }
        build(1,1,n);
        while(m--)
        {
            scanf("%s",test);
            int x,y;
            if(test[0]=='Q')
            {
                scanf("%d%d",&x,&y);
                if(x>y)
                    swap(x,y);
                printf("%d\n",query(1,1,n,x,y));
            }
            else
            {
                scanf("%d%d",&x,&y);
                change(1,1,n,x,y);
            }
        }
    }
    return 0;
}