10分求助（二分答案）

#include<iostream>
#include<algorithm>
using namespace std;
int m,n,a[100010],q;
long long s;
int find(int x){
    int l=1,r=m,mid;
    while(l<=r){
        mid=(l+r)/2;
        if(x<a[mid])r=mid-1;
        else l=mid+1;
    }
    return r;
}
int main(){
    cin>>m>>n;
    for(int i=1;i<=m;i++)cin>>a[i];
    sort(a+1,a+n+1);
    for(int i=1;i<=n;i++){
        cin>>q;
        int k=find(q);
        if(q<=a[1]){
            s+=a[1]-q;
            continue;
        }
        if(q>=a[m]){
            s+=q-a[m];
            continue;
        }
        if(a[k+1]-q>=q-a[k]){
            s+=q-a[k];
        }
        else s+=a[k+1]-q;
    }
    cout<<s;
    return 0;
}