package main

import (
	"bufio"
	"fmt"
	"os"
	"sort"
)

type FastScanner struct {
	r *bufio.Reader
}

func NewFastScanner() *FastScanner {
	return &FastScanner{r: bufio.NewReaderSize(os.Stdin, 1<<20)}
}

func (fs *FastScanner) NextInt64() int64 {
	var sign int64 = 1
	var val int64
	c, err := fs.r.ReadByte()
	for (c < '0' || c > '9') && c != '-' {
		c, err = fs.r.ReadByte()
		if err != nil {
			return 0
		}
	}
	if c == '-' {
		sign = -1
		c, _ = fs.r.ReadByte()
	}
	for c >= '0' && c <= '9' {
		val = val*10 + int64(c-'0')
		c, err = fs.r.ReadByte()
		if err != nil {
			return val * sign
		}
	}
	_ = fs.r.UnreadByte()
	return val * sign
}

func max(a, b int64) int64 {
	if a > b {
		return a
	}
	return b
}

func main() {
	in := NewFastScanner()
	out := bufio.NewWriterSize(os.Stdout, 1<<20)
	defer out.Flush()

	t := int(in.NextInt64())
	for ; t > 0; t-- {
		n := int(in.NextInt64())
		a := make([]int64, n)
		for i := 0; i < n; i++ {
			a[i] = in.NextInt64()
		}
		sort.Slice(a, func(i, j int) bool { return a[i] < a[j] })

		ans := a[n-1] - a[0]

		for i := 0; i+2 < n; i++ {
			ans = max(ans, a[n-1]+a[i+1]-2*a[i])
		}
		for i := 2; i < n; i++ {
			ans = max(ans, 2*a[i]-a[i-1]-a[0])
		}

		fmt.Fprintln(out, ans)
	}
}