description: n people gathered to hold a jury meeting of the upcoming competition, the i-th member of the jury came up with a_i tasks, which they want to share with each other.
  
  First, the jury decides on the order which they will follow while describing the tasks. Let that be a permutation p of numbers from 1 to n (an array of size n where each integer from 1 to n occurs exactly once).
  
  Then the discussion goes as follows:
  
    * If a jury member p_1 has some tasks left to tell, then they tell one task to others. Otherwise, they are skipped. 
    * If a jury member p_2 has some tasks left to tell, then they tell one task to others. Otherwise, they are skipped. 
    * ... 
    * If a jury member p_n has some tasks left to tell, then they tell one task to others. Otherwise, they are skipped. 
    * If there are still members with tasks left, then the process repeats from the start. Otherwise, the discussion ends. 
  
  
  
  A permutation p is nice if none of the jury members tell two or more of their own tasks in a row. 
  
  Count the number of nice permutations. The answer may be really large, so print it modulo 998 244 353.
  
  Input
  
  The first line contains a single integer t (1 ≤ t ≤ 10^4) — the number of test cases.
  
  The first line of the test case contains a single integer n (2 ≤ n ≤ 2 ⋅ 10^5) — number of jury members.
  
  The second line contains n integers a_1, a_2, ..., a_n (1 ≤ a_i ≤ 10^9) — the number of problems that the i-th member of the jury came up with.
  
  The sum of n over all test cases does not exceed 2 ⋅ 10^5.
  
  Output
  
  For each test case, print one integer — the number of nice permutations, taken modulo 998 244 353.
  
  Example
  
  Input
  
  
  4
  2
  1 2
  3
  5 5 5
  4
  1 3 3 7
  6
  3 4 2 1 3 3
  
  
  Output
  
  
  1
  6
  0
  540
  
  Note
  
  Explanation of the first test case from the example:
  
  There are two possible permutations, p = [1, 2] and p = [2, 1]. For p = [1, 2], the process is the following:
  
    1. the first jury member tells a task; 
    2. the second jury member tells a task; 
    3. the first jury member doesn't have any tasks left to tell, so they are skipped; 
    4. the second jury member tells a task. 
  
  
  
  So, the second jury member has told two tasks in a row (in succession), so the permutation is not nice.
  
  For p = [2, 1], the process is the following:
  
    1. the second jury member tells a task; 
    2. the first jury member tells a task; 
    3. the second jury member tells a task. 
  
  
  
  So, this permutation is nice.
solution: import java.util.*;
  import java.util.function.Function;
  import java.util.stream.Collectors;
  
  
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.*;
  import java.math.*;
  
  public class Solution
  {
  	static StringBuilder sb;
  	static dsu dsu;
  	static long fact[];
  	static long m;
  	static long mod;
  	static ArrayList<Integer>prime;
  	static ArrayList<Long>adj[];
  	static int A[],dp[];
  	static int n,k;
  	static ArrayList<Integer>l;
  	static void solve()
      {
  		int n=i();
  		long A[]=new long[n];
  		TreeMap<Long,Integer>h=new TreeMap<>();
  		
  		for(int i=0;i<n;i++) 
  		{
  			A[i]=l();
  			h.put(A[i],h.getOrDefault(A[i],0)+1);
  		}
  		
  		sort(A);
  		
  		
  		long max=h.lastKey();
  		
  		int fre=h.get(max);
  		
  		int less=0;
  		for(int i=0;i<n;i++)
  		{
  			if(max-A[i]>=2)
  			{
  				less++;
  			}
  		}
  		
  		
  		long rem=0;
  		long total=fact[n];
  		if(fre>1)
  		{
  			System.out.println(total);
  			return;
  		}
  		else
  		{
  			rem+=fact[n-1];
  			
  			for(int i=n-2;i>=0;i--)
  			{
  			  
  				int pos=(n-1-i);
  				
  				int sec=(i);
  				long timber=(((fact[sec]*(ncr(less,pos)))%mod)*fact[pos])%mod;
  				
  				rem=(rem+timber)%mod;
  			}
  				
  		}
  		System.out.println((total-rem+mod)%mod);
  		
  		
  		
  		
  		
  		
  		
  		
  		
  		
  		
  		
  		
      }
  	public static void main(String[] args)
  	 {
  		 sb=new StringBuilder();
  		 mod=(long)998244353;
  		 fact=new long[(int)(2*1e5+2)];
  		 fact[0]=fact[1]=1;
  		 for(int i=2;i<fact.length;i++)
  		 {
  			 fact[i]=(i*fact[i-1])%mod;
  		 }
  		 
  		int test=i();
  	    for(int tt=1;tt<=test;tt++) 
  	    {
  	         solve();
  	    }
  	    System.out.println(sb);
  	 }
  	 
  //*******************************************NCR%P*******************************************************	 
  	 static long ncr(int n, int r)
  	 {
  		 if(r>n)
  			return (long)0;
  		 long res=fact[n]%mod;
  		 //System.out.println(res);
  		 res=((long)(res%mod)*(long)(p(fact[r],mod-2)%mod))%mod;
  		 res=((long)(res%mod)*(long)(p(fact[n-r],mod-2)%mod))%mod;
  		 //System.out.println(res);
  		 return res; 
  	 }
  		static long p(long x, long y)//POWER FXN //
  		{
  			if(y==0)
  				return 1;
  			
  			long res=1;
  			while(y>0)
  			{
  				if(y%2==1)
  				{
  					res=(res*x)%mod;
  					y--;
  				}
  				
  				x=(x*x)%mod;
  				y=y/2;
  				
  				
  			}
  			return res;
  		}
  		static long ceil(long num, long den)
  		{
  			return (long)(num+den-1)/den;
  		}
  		
  
  //*******************************************END*******************************************************
  		static int LowerBound(long a[], long x, int i, int j) 
  		{ 
  			//X is the key value
  			int l=i;int r=j;
  			int lb=-1;
  			  while(l<=r)
  			  {
  			    int m=(l+r)/2;
  			    
  			    if(a[m]>=x) 
  			    {
  			    	lb=m;
  			    	r=m-1;
  			    }
  			    else l=m+1;
  			  }
  			  return lb;
  		}
  		static int UpperBound(long a[], long x, int i, int j) 
  		{// x is the key or target value
  		    int l=i,r=j;
  		    int ans=-1;
  		    while(l<=r)
  		    {
  		       int m=(l+r)/2;
  		       
  		       if(a[m]<=x) 
  		       {
  		    	   ans=m;
  		    	   l=m+1;
  		       }
  		       else r=m-1;
  		    }
  		    return ans;
  		 }
  		
  		
  		
  	 
  	 
  	 //*********************************Disjoint set union*************************//
  	 static class dsu
  	 {
  		 int parent[];
  		 dsu(int n)
  		 {
  			 parent=new int[n+1];
  			 for(int i=0;i<=n;i++)
  				 parent[i]=-1;
  		 }
  		 int find(int a)
  		 {
  			 if(parent[a]<0)
  				 return a;
  			 else
  			 {
  				 int x=find(parent[a]);
  				 parent[a]=x;
  				 return x;
  			 }
  		 }
  		 void merge(int a,int b)
  		 {
  			 a=find(a);
  			 b=find(b);
  			 if(a==b)
  				 return;
  			 parent[b]=a;
  		 }
  	 }
  	 
  	 
  	 
  //*******************************************PRIME FACTORIZE *****************************************************************************************************//
  	 static TreeMap<Integer,Integer> prime(long n)
  	 {
  		 TreeMap<Integer,Integer>h=new TreeMap<>();
  		 long num=n;
  		 for(int i=2;i<=Math.sqrt(num);i++)
  		 {
  			 if(n%i==0)
  			 {
  				 int nt=0;
  				 while(n%i==0) {
  					 n=n/i;
  					 nt++;
  				 }
  				 h.put(i, nt);
  			 }
  		 }
  		 if(n!=1)
  			 h.put((int)n, 1);
  		 return h;
  		 
  	 }
  	 
  	
  	
  //*************CLASS PAIR ***********************************************************************************************************************************************
  	   
  	 
  	 static class pair implements Comparable<pair>
  	    {
  	        long x;
  	        int y;
  	       
  	        pair(long x, int y) {
  	            this.x = x;
  	            this.y = y;
  	          
  	        }
  	        public int compareTo(pair o)
  	        {
  	        	return(int) (y-o.y);
  	        	
  	        }
  	        
  	         public boolean equals(Object o) 
  	         { 
  	             if (this == o) { 
  	                 return true; 
  	             } 
  	             if (o == null) { 
  	                 return false; 
  	             } 
  	             if (this.getClass() != o.getClass()) { 
  	                 return false; 
  	             } 
  	             pair other = (pair)o; 
  	             if (this.x != other.x || this.y!=other.y) { 
  	                 return false; 
  	             } 
  	             return true; 
  	         }
  	    } 
  	        
  	        
  			
  //*************CLASS PAIR *****************************************************************************************************************************************************
  	
  	
  	
  
      static class InputReader {
          private InputStream stream;
          private byte[] buf = new byte[1024];
          private int curChar;
          private int numChars;
          private SpaceCharFilter filter;
  
          public InputReader(InputStream stream) {
              this.stream = stream;
          }
  
          public int read() {
              if (numChars == -1)
                  throw new InputMismatchException();
              if (curChar >= numChars) {
                  curChar = 0;
                  try {
                      numChars = stream.read(buf);
                  } catch (IOException e) {
                      throw new InputMismatchException();
                  }
                  if (numChars <= 0)
                      return -1;
              }
              return buf[curChar++];
          }
  
          public int Int() {
              int c = read();
              while (isSpaceChar(c))
                  c = read();
              int sgn = 1;
              if (c == '-') {
                  sgn = -1;
                  c = read();
              }
              int res = 0;
              do {
                  if (c < '0' || c > '9')
                      throw new InputMismatchException();
                  res *= 10;
                  res += c - '0';
                  c = read();
              } while (!isSpaceChar(c));
              return res * sgn;
          }
  
          public String String() {
              int c = read();
              while (isSpaceChar(c))
                  c = read();
              StringBuilder res = new StringBuilder();
              do {
                  res.appendCodePoint(c);
                  c = read();
              } while (!isSpaceChar(c));
              return res.toString();
          }
  
          public boolean isSpaceChar(int c) {
              if (filter != null)
                  return filter.isSpaceChar(c);
              return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
          }
  
          public String next() {
              return String();
          }
  
          public interface SpaceCharFilter {
              public boolean isSpaceChar(int ch);
          }
      }
  
      static class OutputWriter {
          private final PrintWriter writer;
  
          public OutputWriter(OutputStream outputStream) {
              writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(outputStream)));
          }
  
          public OutputWriter(Writer writer) {
              this.writer = new PrintWriter(writer);
          }
  
          public void print(Object... objects) {
              for (int i = 0; i < objects.length; i++) {
                  if (i != 0)
                      writer.print(' ');
                  writer.print(objects[i]);
              }
          }
  
          public void printLine(Object... objects) {
              print(objects);
              writer.println();
          }
  
          public void close() {
              writer.close();
          }
  
          public void flush() {
              writer.flush();
          }
      }
  
      static InputReader in = new InputReader(System.in);
      static OutputWriter out = new OutputWriter(System.out);
     
  
      public static int[] sort(int[] a) {
          int n = a.length;
          ArrayList<Integer> l = new ArrayList<>();
          for (int i : a)
              l.add(i);
          Collections.sort(l);
          for (int i = 0; i < l.size(); i++)
              a[i] = l.get(i);
          return a;
      }
      public static long[] sort(long[] a) {
          int n = a.length;
          ArrayList<Long> l = new ArrayList<>();
          for (long i : a)
              l.add(i);
          Collections.sort(l);
          for (int i = 0; i < l.size(); i++)
              a[i] = l.get(i);
          return a;
      }
  
      public static long pow(long x, long y) {
          long res = 1;
          while (y > 0) {
              if (y % 2 != 0) {
                  res = (res * x);// % modulus;
                  y--;
  
              }
              x = (x * x);// % modulus;
              y = y / 2;
          }
          return res;
      }
  //GCD___+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
      public static long gcd(long x, long y) {
          if (x == 0)
              return y%mod;
          else
              return gcd(y % x, x);
      }
      //****************LOWEST COMMON MULTIPLE   *************************************************************************************************************************************
  
      public static long lcm(long x, long y) {
          return (x * (y / gcd(x, y)));
      }
  //INPUT PATTERN******************************************************************************************************************************************************************
      public static int i() {
          return in.Int();
      }
  
      public static long l() {
          String s = in.String();
          return Long.parseLong(s);
      }
  
      public static String s() {
          return in.String();
      }
  
      public static int[] readArray(int n) {
          int A[] = new int[n];
          for (int i = 0; i < n; i++) {
              A[i] = i();
          }
          return A;
      }
  
      public static long[] readArray(long n) {
          long A[] = new long[(int) n];
          for (int i = 0; i < n; i++) {
              A[i] = l();
          }
          return A;
      }
      public int[][] deepCopy(int[][] matrix) {
  		return java.util.Arrays.stream(matrix).map(el -> el.clone()).toArray($ -> matrix.clone());
  		}
   
  
  }
  
  
  
  
  
  
  	