线段树TLE了……

#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<cmath>
#include<iostream>
#include<algorithm>
#include<queue>
#include<map>
#define inf 0x7fffffff
#define ll long long
#define N 100005
using namespace std;
int ra()
{
    int x=0,f=1; char ch=getchar();
    while (ch<'0' || ch>'9') {if (ch=='-') f=-1; ch=getchar();}
    while (ch>='0' && ch<='9') {x=x*10+ch-'0'; ch=getchar();}
    return x*f;
}
struct node{
    int l,r,mx,mn;
}t[N<<1];
int a[N],n,q;
void update(int k)
{
    t[k].mx=max(t[k<<1].mx,t[k<<1|1].mx);
    t[k].mn=min(t[k<<1].mn,t[k<<1|1].mn);
}
void build(int k ,int l, int r)
{
    t[k].l=l; t[k].r=r;
    if (l==r)
    {
        t[k].mn=t[k].mx=a[l];
        return;
    }
    int mid=(l+r)>>1;
    build(k<<1,l,mid); build(k<<1|1,mid+1,r);
    update(k);
}
int askmax(int k, int x, int y)
{
    int l=t[k].l,r=t[k].r;
    if (x==l && y==r) return t[k].mx;
    int mid=(l+r)>>1;
    if (y<=mid) return askmax(k<<1,x,y);
    else if (x>mid) return askmax(k<<1|1,x,y);
    else return max(askmax(k<<1,x,mid),askmax(k<<1|1,mid+1,y));
}
int askmin(int k, int x, int y)
{
    int l=t[k].l,r=t[k].r;
    if (x==l && y==r) return t[k].mn;
    int mid=(l+r)>>1;
    if (y<=mid) return askmin(k<<1,x,y);
    else if (x>mid) return askmin(k<<1|1,x,y);
    else return min(askmin(k<<1,x,mid),askmin(k<<1|1,mid+1,y));
}
int main()
{
    n=ra();q=ra(); 
    for (int i=1; i<=n; i++) a[i]=ra();
    build(1,1,n);
    for (int i=1; i<=q; i++)
    {
        int x=ra(),y=ra();
        cout<<askmax(1,x,y)-askmin(1,x,y)<<endl;
    }
    return 0;
最后那个大括号懒得打了