Balanced Lineup——区间最大值、区间最小值

#include<iostream>
#include<stdio.h>
#include<math.h>
#include<algorithm>
#include<vector>
#include<map>
using namespace std;
typedef long long ll;
const int maxn=1e5+5;
struct node
{
    int l,r;
    int minn,maxx;
} tree[maxn<<2];
int n,a[maxn],q;
void push_up(int x)
{
    tree[x].maxx=max(tree[x<<1].maxx,tree[x<<1|1].maxx);
    tree[x].minn=min(tree[x<<1].minn,tree[x<<1|1].minn);
}
void build(int x,int l,int r)
{
    tree[x].l=l,tree[x].r=r;
    if(l==r)
    {
        tree[x].maxx=tree[x].minn=a[l];
    }
    else
    {
        int mid=(l+r)>>1;
        build(x<<1,l,mid);
        build(x<<1|1,mid+1,r);
        push_up(x);
    }
}
ll query(int x,int l,int r,int flag)
{
    int L=tree[x].l,R=tree[x].r;

    if(l<=L && R<=r)
    {
        if(flag)return tree[x].maxx;
        else return tree[x].minn;
    }
    else
    {

        if(flag)
        {
            ll ans=0;
            int mid=(L+R)>>1;
            if(mid>=l)ans=max(ans,query(x<<1,l,r,flag));
            if(mid<r)ans=max(ans,query(x<<1|1,l,r,flag));
            push_up(x);
            return ans;
        }
        else
        {
            ll ans=0x3f3f3f3f;
            int mid=(L+R)>>1;
            if(mid>=l)ans=min(ans,query(x<<1,l,r,flag));
            if(mid<r)ans=min(ans,query(x<<1|1,l,r,flag));
            push_up(x);
            return ans;
        }

    }

}
int main()
{
    scanf("%d%d",&n,&q);
    for(int i=1; i<=n; i++)
        scanf("%d",&a[i]);
    build(1,1,n);
    for(int i=1; i<=q; i++)
    {
        int l,r;
        scanf("%d%d",&l,&r);
        ll ans=query(1,l,r,1)-query(1,l,r,0);
        printf("%lld\n",ans);
    }
    return 0;
}