#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());
 
        // delta = floor(k/2)
        ll delta = k / 2;
 
        // If delta > n-1, no valid x
        if (delta > n - 1) {
            cout << 0 << "\n";
            continue;
        }
 
        // Left endpoint = b[delta], right endpoint = b[n-1-delta]
        ll L = b[delta];
        ll R = b[n - 1 - delta];
        // The interval of valid x is [L..R], inclusive.
        ll ans = max(0LL, R - L + 1);
        cout << ans << "\n";
    }
    return 0;
}
 

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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