HDU1754 I Hate It 点修改 区间查询 模板题

#include <cstdio>//大白书上说节点数最多有2*n-1个 n为区间长度 
#include <cstring>//这个题开420000的数组却RE了 换成100W+就过了……sad
#include <cstdlib>
#include <algorithm>
#include <iostream>


using namespace std;

int st[1048576];
int gr[210000];

int max(int x,int y)
{
    return x>=y ? x:y;
}

int creat(int node,int l,int r)
{
    if(l == r)
    {
        st[node] = gr[l];
        return st[node];
    }
    int m = (l+r)/2;

    st[node] = max(creat(node+node,l,m),creat(node+node+1,m+1,r));

    return st[node];
}

int query(int ml,int mr,int node,int l,int r)
{
    if(ml == l && mr == r)
        return st[node];
    int m = (l+r)/2;
    if(mr <= m)
    {
        return query(ml,mr,node+node,l,m);
    }
    if(m < ml)
    {
        return query(ml,mr,node+node+1,m+1,r);
    }
    return max(query(ml,m,node+node,l,m),query(m+1,mr,node+node+1,m+1,r));
}

int change(int site,int grade,int node,int l,int r)
{
    if(l == r && r == site)
    {
        st[node] = grade;
        return st[node];
    }
    int m = (l+r)/2;
    if(site <= m)
    {
        st[node] = change(site,grade,node+node,l,m);
        return st[node];
    }
    if(m < site)
    {
        st[node] = change(site,grade,node+node+1,m+1,r);
        return st[node];
    }
}

int q[110];
void output(int n)
{
    int t;
    int s = 0,e = 1;
    q[0] = 1;
    int i = 1,j = 1;
    while(1)
    {

        t = q[s++];
        printf("st[%d] = %d ",t,st[t]);
        q[e++] = t+t;
        q[e++] = t+t+1;
        if(t == n+n-1) break;
        if(i == j)
        {
            i = 1;
            j *= 2;
            printf("\n");
        }
        else i++;
    }
}

int main()
{
    int n,m,T;
    int i;
    char order[5];
    int l,r;
    int site ,grade;

    while(scanf("%d %d",&n,&m) != EOF)
    {
        for(i = 1;i <= n; i++)
            scanf("%d",&gr[i]);

        creat(1,1,n);
        //output(n);

        while(m--)
        {
            scanf("%s",order);
            if(order[0] == 'Q')
            {
                scanf("%d %d",&l,&r);
                printf("%d\n",query(l,r,1,1,n));
                //output(n);
            }
            else if(order[0] == 'U')
            {
                scanf("%d %d",&site,&grade);
                change(site,grade,1,1,n);
                //output(n);
            }
        }
    }
    return 0;
}