80分求条

#include<bits/stdc++.h>
#define int long long
using namespace std;
int m,n;
int a[1000001],b[1000001],ans=0;
signed main()
{
	//freopen("xx.in","r",stdin);
	//freopen(".out","w",stdout);
	cin>>m>>n;
	for(int i=1; i<=m; i++)
	{
		cin>>a[i];
	}
	for(int i=1; i<=n; i++)
	{
		cin>>b[i];
	}
	a[0]=-1e9;
	a[m+1]=1e9;
	sort(a+1,a+m+1);
	for(int i=1; i<=n; i++)
	{
		int l=1,r=m;
		int mid,res,s=1e10;
		while(l<=r)
		{
			mid=(l+r)/2;
			if(a[mid]>=b[i])
			{
				s=min(s,a[mid]-b[i]);
				r=mid-1;
				res=mid;
			}
			else if(a[mid]<b[i])
			{
				s=min(s,b[i]-a[mid]);
				l=mid+1;
			}
			else
			{
				s=0;
				res=mid;
				break;
			}
		}
		ans+=min(abs(a[res]-b[i]),abs(b[i]-a[res-1]));
	}
	cout<<ans;
	return 0;
}