package main

import (
	"bufio"
	"os"
	"sort"
	"strconv"
)

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 1024*1024), 10*1024*1024)

	nextInt := func() int {
		scanner.Scan()
		val, _ := strconv.Atoi(scanner.Text())
		return val
	}

	writer := bufio.NewWriter(os.Stdout)
	defer writer.Flush()

	if !scanner.Scan() {
		return
	}
	t, _ := strconv.Atoi(scanner.Text())

	for i := 0; i < t; i++ {
		n := nextInt()
		k := nextInt()

		a := make([]int, n)
		for j := 0; j < n; j++ {
			a[j] = nextInt()
		}

		sort.Ints(a)

		minM := n - k
		if minM%2 != 0 {
			minM++
		}

		if minM > n {
			writer.WriteString("1\n")
		} else {
			c := minM / 2
			ans := a[n-c] - a[c-1] + 1
			writer.WriteString(strconv.Itoa(ans) + "\n")
		}
	}
}