// ---------- begin scannner ---------- #[allow(dead_code)] mod scanner { use std::str::FromStr; pub struct Scanner<'a> { it: std::str::SplitWhitespace<'a>, } impl<'a> Scanner<'a> { pub fn new(s: &'a String) -> Scanner<'a> { Scanner { it: s.split_whitespace(), } } pub fn next(&mut self) -> T { self.it.next().unwrap().parse::().ok().unwrap() } pub fn next_bytes(&mut self) -> Vec { self.it.next().unwrap().bytes().collect() } pub fn next_chars(&mut self) -> Vec { self.it.next().unwrap().chars().collect() } pub fn next_vec(&mut self, len: usize) -> Vec { (0..len).map(|_| self.next()).collect() } } } // ---------- end scannner ---------- use std::io::Write; use std::collections::*; type Map = BTreeMap; type Set = BTreeSet; type Deque = VecDeque; fn main() { use std::io::Read; let mut s = String::new(); std::io::stdin().read_to_string(&mut s).unwrap(); let mut sc = scanner::Scanner::new(&s); let out = std::io::stdout(); let mut out = std::io::BufWriter::new(out.lock()); run(&mut sc, &mut out); } fn run(sc: &mut scanner::Scanner, out: &mut std::io::BufWriter) { let t: u32 = sc.next(); for _ in 0..t { let n: usize = sc.next(); let mut a: Vec = sc.next_vec(n); a.sort(); let ans = if n % 2 == 0 { a.chunks(2).map(|a| a[1] - a[0]).sum::() } else { let mut ans = a[n / 2]; let mut geta = 0; for i in 1..=(n / 2) { geta += a[n - 2 * i + 1] - a[n - 2 * i]; ans = ans.max(a[(n - 2 * i) / 2] + geta); } ans }; writeln!(out, "{}", ans).ok(); } }