[Usaco2016 Dec]Counting Haybales

Original title link https://www.lydsy.com/JudgeOnline/problem.php?id=4747

First the original array is sorted, then binary search can be. Time complexity \ (O ((N + Q) logN) \) .

#include<algorithm>
#include<iostream>
#include<cstring>
#include<cstdio>
#define maxn 100010
using namespace std;
 
inline int read(){
    register int x(0),f(1); register char c(getchar());
    while(c<'0'||'9'<c){ if(c=='-') f=-1; c=getchar(); }
    while('0'<=c&&c<='9') x=(x<<1)+(x<<3)+(c^48),c=getchar();
    return x*f;
}
 
int a[maxn];
int n,m;
 
int main(){
    n=read(),m=read();
    for(register int i=1;i<=n;i++) a[i]=read();
    sort(a+1,a+1+n);
    for(register int i=1;i<=m;i++){
        int x=read(),y=read();
        if(x>y) swap(x,y);
        int l=lower_bound(a+1,a+1+n,x)-a;
        int r=upper_bound(a+1,a+1+n,y)-a;
        printf("%d\n",r-l);
    }
    return 0;
}