#include <bits/stdc++.h>
using namespace std;
 
void solve() {
    int n, k;
    cin >> n >> k;
    vector<int> a(n);
    for (int& x : a) cin >> x;
    sort(a.begin(), a.end());
 
    int l = (n - k - 1) / 2;              // floor((n - k - 1)/2)
    int r = (n + k) / 2;                  // floor((n + k)/2)
 
    cout << a[r] - a[l] + 1 << '\n';      // number of possible medians
}
 
int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int t; cin >> t;
    while (t--) solve();
}
 

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NAo0IDAKMSAyIDMgNAo1IDIKNyA2IDYgNyAxCjMgMQo2IDcgOQo2IDIKNSAxIDkgMTAgMTMgMgo=

4
4 0
1 2 3 4
5 2
7 6 6 7 1
3 1
6 7 9
6 2
5 1 9 10 13 2