二分,找最接近他的数字

#include<iostream>
#include<algorithm>
using namespace std;
#define ll long long
const int N = 1e5 + 5;
ll m, n, ans;
ll a[N], b[N];
ll Next(ll l) {
	ll x = a[l];
	for (ll i = l + 1; i <= m; ++i) {
		if (a[i] != x)return  a[i];
	}
	return x;
}
ll lbreach(ll x) {
	ll l = 0, r = m, mid;
	while (l < r) {
		mid = (l + r) >> 1;
		if (a[mid] >= x)r = mid;
		else l = mid + 1;//就是本坐标
	}
	if (a[l] == x) return 0;
	if (l == 1) return a[1] - x;
	ll Numnext = Next(l - 1);
	return min(abs(Numnext - x), abs(a[l - 1] - x));
}
int main() {
	scanf("%lld%lld", &m, &n);
	for (ll i = 1; i <= m; ++i)scanf("%lld", &a[i]);
	for (ll i = 1; i <= n; ++i)scanf("%lld", &b[i]);
	sort(a + 1, a + 1 + m);
	for (ll i = 1; i <= n; ++i) {
		ans += lbreach(b[i]);
	}
	printf("%lld\n", ans);
	return 0;
}