使用双指针进行模拟即可。

AC code：

#include <bits/stdc++.h>
using namespace std;
#define ll long long

int main() {
    int n, k;
    cin >> n >> k;
    vector<ll> a(n);
    for (int i = 0; i < n; i++) {
        cin >> a[i];
    }
    sort(a.begin(), a.end());
    int max_len = 0;
    int i = 0;
    for (int j = 0; j < n; j++) {
        while (a[j] - a[i] > k) {
            i++;
        }
        if (j - i + 1 > max_len) {
            max_len = j - i + 1;
        }
    }
    cout << max_len << endl;
    return 0;
}

注意到「最大值与最小值的差」这一函数有单调性，上双指针即可。

#include <bits/stdc++.h>
using namespace std;
int a[200012];
int main()
{
    int n, k;
    cin >> n >> k;
    for (int i = 1; i <= n; i++)
        cin >> a[i];
    sort(a + 1, a + n + 1);
    int r = 1, ans = 1;
    for (int i = 1; i <= n - 1; i++)
    {
        while (r < n && a[r + 1] - a[i] <= k) r++;
        ans = max(ans, r - i + 1);
    }
    cout << ans << endl;
    return 0;
}