POJ3264线段树求最值

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<ctype.h>
#include<cstring>
using namespace std;

const int maxn=50005;
inline int read()
{
    int x=0,w=0;char c=getchar();
    while(!isdigit(c))w|=c==‘-‘,c=getchar();
    while(isdigit(c))x=(x<<3)+(x<<1)+(c^48),c=getchar();
    return w?-x:x;
}
struct SegmentTree
{
    struct Node{
        int l,r;
        int mx,mn;
        int tagmx,tagmn;
    }e[4*maxn];
    #define ls (ro<<1)
    #define rs (ro<<1|1)
    #define INF 0x3f3f3f3f
    
    int maxx,minn;
    int n,m;
    void build(int ro,int l,int r)
    {
        e[ro].l=l,e[ro].r=r;
        e[ro].mn=INF,e[ro].mx=-INF;
        if(l==r)return ;
        int mid=(l+r)>>1;
        build(ls,l,mid);
        build(rs,mid+1,r);
    }
    void insert(int ro,int i,int k)
    {
        if(e[ro].l==e[ro].r){
            e[ro].mx=e[ro].mn=k;return;
        }
        e[ro].mn=min(e[ro].mn,k);
        e[ro].mx=max(e[ro].mx,k);
        int mid=(e[ro].l+e[ro].r)>>1;
        if(i<=mid)insert(ls,i,k);
        else insert(rs,i,k);
    }
    void query(int ro,int l,int r)
    {
        if(e[ro].mn>=minn and e[ro].mx<=maxx)return ;
        if(e[ro].l==l and e[ro].r==r){
            minn=min(minn,e[ro].mn);
            maxx=max(maxx,e[ro].mx);
            return;
        }
        int mid=(e[ro].l+e[ro].r)>>1;
        if(r<=mid)query(ls,l,r);
        else if(l>mid)query(rs,l,r);
        else {query(ls,l,mid);query(rs,mid+1,r);}
    }
    inline void getans()
    {
        n=read();m=read();
        build(1,1,n);
        for(int i=1;i<=n;i++)
            insert(1,i,read());
        for(int i=1;i<=m;i++)
        {
            maxx=-INF,minn=INF;
            int l=read(),r=read();
            query(1,l,r);
            printf("%d\n",maxx-minn);
        }
        return ;
    }
    #undef ls
    #undef rs
    #undef INF
}st;
int main()
{
    st.getans();
    return 0;
}