50 pts 求助

#include<bits/stdc++.h>
using namespace std;
int m, n, a[100010], b[100010], res = 0;

int main()
{
    cin >> m >> n;
    for(int i=0; i<m; i++)
    {
        cin >> a[i];
    }
    for(int i=0; i<n; i++)
    {
        cin >> b[i];
    }
    sort(a + 0, a + m);
    for(int i=0; i<n; i++)
    {
        int l = 0, r = m - 1, ans = 1e6 + 10;
        while(l < r)
        {
            int mid = (l + r) / 2;
            if(a[mid] >= b[i]) ans = min(ans, abs(b[i] - a[mid])), r = mid;
            else l = mid + 1, ans = min(ans, abs(b[i] - a[mid]));
        }
        res += ans;
    }
    printf("%d", res);
    return 0;
}