#include <bits/stdc++.h>
using namespace std;
using ll = long long;
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
int t;
cin >> t;
while (t--) {
int n;
ll k;
cin >> n >> k;
vector<ll> b(n);
for (int i = 0; i < n; i++) {
cin >> b[i];
}
// Sort bar‐positions
sort(b.begin(), b.end());
int L = (n - k + 1) / 2;
int R = (n + k + 2) / 2;
cout << b[R] - b[L] + 1 << '\n';
}
return 0;
}
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