2020西工大校赛 A张经理的员工（二分）

#include<iostream>
#include<algorithm>
using namespace std;
const int N=1e5+10;
int a[N],sum[N];
int main(){
    int n;
    int i;
    int m;
    cin>>n>>m;
    for(i=1;i<=n;i++){
        scanf("%d",&a[i]);
    }
    sort(a+1,a+1+n);
    for(i=1;i<=n;i++)
        sum[i]=sum[i-1]+a[i];
    while(m--){
        int l,r;
        scanf("%d%d",&l,&r);
        if(l>r)
            swap(l,r);
        int mid=(l+r)/2;
        int pos=upper_bound(a+1,a+1+n,mid)-a-1;
        int pos1=upper_bound(a+1,a+1+n,l)-a-1;
        int pos2=upper_bound(a+1,a+1+n,r)-a-1;
        long long ans=0;
         ans+=sum[pos]-sum[pos1]-(pos-pos1)*l;
        ans+=l*(pos1)-sum[pos1];
        ans+=r*(pos2-pos)-(sum[pos2]-sum[pos]);
        ans+=sum[n]-sum[pos2]-r*(n-pos2);
        cout<<ans<<endl;
    }
}