CF1409E AC

#include <assert.h>
#include <bits/stdc++.h>
using namespace std;
#define dbg(...) logger(#__VA_ARGS__, __VA_ARGS__)
template <typename... Args> void logger(string vars, Args &&... values)
{
    cerr << vars << " = ";
    string delim = "";
    (..., (cerr << delim << values, delim = ", "));
    cerr << endl;
}

template <class T> inline auto vv(int m) { return vector<vector<T>>(m, vector<T>(m)); }
template <class T> inline auto vv(int m, int n) { return vector<vector<T>>(m, vector<T>(n)); }
template <class T, T init> inline auto vv(int m) { return vector<vector<T>>(m, vector<T>(m, init)); }
template <class T, T init> inline auto vv(int m, int n) { return vector<vector<T>>(m, vector<T>(n, init)); }

template <class T> using mpq = priority_queue<T, vector<T>, greater<T>>;

using ll = long long;
using pii = pair<int, int>;
using vl = vector<ll>;
using vi = vector<int>;

int main(int argc, char **argv)
{
    int t;
    cin >> t;
    while (t--) {
        int n, k;
        cin >> n >> k;
        vi a(n), b(n);
        for (auto &x : a)
            cin >> x;
        for (auto &x : b)
            cin >> x;

        sort(a.begin(), a.end());
        vi one_pass(n);
        vi max_op(n);
        for (int i = 0; i < n; ++i)
            one_pass[i] = upper_bound(a.begin(), a.end(), a[i]) - lower_bound(a.begin(), a.end(), a[i] - k);
        max_op[0] = one_pass[0];
        for (int i = 1; i < n; ++i)
            max_op[i] = max(max_op[i - 1], one_pass[i]);
        int ans = 0;
        for (int i = 0; i < n; ++i) {
            int op_id = lower_bound(a.begin(), a.end(), a[i] - k) - a.begin() - 1;
            int best = (op_id >= 0 ? max_op[op_id] : 0) + one_pass[i];
            ans = max(ans, best);
        }
        cout << ans << endl;
    }
    return 0;
};