TopologicalOrder.java

import java.util.*;
import java.lang.*;
import java.io.*;
import java.math.*;
/*
 * Author    : joney_000[let_me_start]
 * Algorithm : Maximum matching for bipartite graph. Hopcroft-Karp algorithm in O(E * sqrt(V))
 * Platform  : https://www.facebook.com/hackercup
 *
 */

/*    The Main Class                */
public class A{
	
	private InputStream inputStream ;
	private OutputStream outputStream ;
	private FastReader in ;
    	private PrintWriter out ;
	/*
		Overhead [Additional Temporary Strorage] but provides memory reusibility for multiple test cases.
		Size Limit : 10^5 + 4 
	*/
	private final int BUFFER = 100005;
	private int    tempints[] = new int[BUFFER];
	private long   templongs[] = new long[BUFFER];
	private double tempdoubles[] = new double[BUFFER];
	private char   tempchars[] = new char[BUFFER];
	private final long mod = 1000000000+7;
	private final int  INF  = Integer.MAX_VALUE / 10;
	private final long INF_L  = Long.MAX_VALUE / 10;
	
	public A(){}
	public A(boolean stdIO)throws FileNotFoundException{
		//stdIO = false;
		if(stdIO){
			inputStream = System.in;
			outputStream = System.out;
		}else{
			inputStream = new FileInputStream("laundro_matt.txt");
			outputStream = new FileOutputStream("output.txt");
		}
		in = new FastReader(inputStream);
		out = new PrintWriter(outputStream);
		
	}
	final int MAXV = 6;//critical
	int v = 0;
	boolean vis [] = new boolean [MAXV+1];
	int order[] = new int [MAXV + 1];
	LinkedList<Integer> adj[] = new LinkedList[MAXV+1];
	Stack stack = new Stack();
	int idx = 1;
  	void run()throws Exception{
	
		 int tests = i();
		 once();
		 for(int t  = 1 ; t<= tests ; t++){
		 	v= i(); int e = i();
		 	clear();
		 	for(int i = 1 ; i<= e ;i++){
		 		int u = i(); int v = i();
		 		adj[u].add(v); //  
		 	}
		 	topoSort();
			printOrder();
			//out.write("Case #"+t+": "+ans+"\n");	
		 	
		}//end tests
	}//end run
	void once(){
		for(int i  =1 ; i<= MAXV ; i++)
			adj[i] = new LinkedList<Integer>();	
	}	
	void clear(){
		idx = 1;
		Arrays.fill(vis, 1, v+1, false);
    		stack.clear();
    		for(int i = 1 ; i<= v; i++)adj[i].clear();
    	}
    	void topoSort(){
    	
	  for (int i = 1; i <= v; i++){
            if (!vis[i])dfs(i);
 	  }
        
        while (!stack.empty())order[idx++] = (int)stack.pop();
      
      }
      void dfs(int u){
        
        vis[u] = true;
        Integer v;
        Iterator<Integer> it = adj[u].iterator();
        while (it.hasNext()){
            v = it.next();
            if(!vis[v])
                dfs(v);
        }
        // Push current vertex to stack which stores result
        stack.push(new Integer(u));
      }
      
	void printOrder(){
		for(int i = 1 ; i<= v ; i++)out.write(""+order[i]+" ");
	}
//****************************** My Utilities ***********************//
 	void print_r(Object... o){
       	out.write("\n"+Arrays.deepToString(o)+"\n");
        	out.flush();
	}

 	boolean isPrime(long n){
  		if(n==1)return false;
  		if(n<=3)return true;
  		if(n%2==0)return false;
  		for(int i=2 ;i <= Math.sqrt(n); i++){
   			if(n%i==0)return false;
  		}
  		return true;
 	}
 	// sieve
 	int[] primes(int n){       // for(int i=1;i<=arr.length-1;i++)out.write(""+arr[i]+" ");
  		boolean arr[] = new boolean[n+1];
  		Arrays.fill(arr,true);
  		arr[1]=false;
  		for(int i=2;i<=Math.sqrt(n);i++){
			if(!arr[i])continue;
			for(int j = 2*i ;j<=n;j+=i){
				arr[j]=false;
			}
  		}
  		LinkedList<Integer> ll = new LinkedList<Integer>();
  		for(int i=1;i<=n;i++){	
   			if(arr[i])ll.add(i);
  		}
  		n = ll.size();
  
  		int primes[] = new int[n+1];
  		for(int i=1;i<=n;i++){
    			primes[i]=ll.removeFirst();
  		}
  		return primes;
 	}
 	long gcd(long a , long b){
  		if(b==0)return a;
  		return gcd(b , a%b);
 	}
 	long lcm(long a , long b){
  		if(a==0||b==0)return 0;
  		return (a*b)/gcd(a,b);
 	}
 	long mulmod(long a , long b ,long mod){
  		if(a==0||b==0)return 0;
  		if(b==1)return a;
   		long ans = mulmod(a,b/2,mod);
   		ans = (ans*2)% mod;
   		if(b%2==1)ans = (a + ans)% mod;
   		return ans;
 	}
 	long pow(long a , long b ,long mod){
   		if(b==0)return 1;
  		if(b==1)return a;
   		long ans = pow(a,b/2,mod);
   		ans = (ans * ans);
   		if(ans >= mod )ans %= mod;
   		
   		if(b%2==1)ans = (a * ans);
   		if(ans >= mod )ans %= mod;
   		
   		return ans;
 	}
 	// 20*20   nCr Pascal Table
 	long[][] ncrTable(){
  		long ncr[][] = new long[21][21];
  		for(int i=0 ;i<=20 ;i++){ncr[i][0]=1;ncr[i][i]=1;}
  		for(int j=0;j<=20 ;j++){
   			for(int i=j+1;i<= 20 ;i++){
    				ncr[i][j] = ncr[i-1][j]+ncr[i-1][j-1];
   			}
  		}
  	return ncr;
 	}
	//*******************************I/O******************************//	
	int i()throws Exception{
 		//return Integer.parseInt(br.readLine().trim());
 		return in.nextInt();
	}
	int[] is(int n)throws Exception{
  //int arr[] = new int[n+1];
  		for(int i=1 ; i <= n ;i++)tempints[i] = in.nextInt();  
 		return tempints;
	}
	long l()throws Exception{
 		return in.nextLong();
	}
	long[] ls(int n)throws Exception{
 		for(int i=1 ; i <= n ;i++)templongs[i] = in.nextLong();  
 		return templongs;
	}

	double d()throws Exception{
 		return in.nextDouble();
	}
	double[] ds(int n)throws Exception{
  		for(int i=1 ; i <= n ;i++)tempdoubles[i] = in.nextDouble();  
 		return tempdoubles;
	}
	char c()throws Exception{
 		return in.nextCharacter();
	}
	char[] cs(int n)throws Exception{
  		for(int i=1 ; i <= n ;i++)tempchars[i] = in.nextCharacter();  
 		return tempchars;
	}
	String s()throws Exception{
 		return in.nextLine();
	}
	BigInteger bi()throws Exception{
 		return in.nextBigInteger();
	}
//***********************I/O ENDS ***********************//
//*********************** 0.3%f [precision]***********************//
/* roundoff upto 2 digits 
   double roundOff = Math.round(a * 100.0) / 100.0;
                    or
   System.out.printf("%.2f", val);
					
*/
/*
  print upto 2 digits after decimal
  val = ((long)(val * 100.0))/100.0;
  
*/    private void closeResources(){
		 	 out.flush();
    		 out.close();
    		 return;
	}
	public static void main(String[] args) throws java.lang.Exception{
		//let_me_start Shinch Returns 
		
 
    /*  
    	  // Old Reader Writer
    	  BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
        BufferedWriter out=new BufferedWriter(new OutputStreamWriter(System.out));
	  BufferedReader br=new BufferedReader(new FileReader("input.txt"));
        BufferedWriter out=new BufferedWriter(new FileWriter("output.txt"));
    */ 	 
    		 A driver = new A(true);
    		 long start =  System.currentTimeMillis();
    		 driver.run();
    		 long end =  System.currentTimeMillis();
    		 //out.write(" Total Time : "+(end - start)+"\n");
    		 driver.closeResources();
    		 return ;
    		 
	}	 

}

class FastReader{

	private boolean finished = false;

	private InputStream stream;
	private byte[] buf = new byte[4*1024];
	private int curChar;
	private int numChars;
	private SpaceCharFilter filter;

	public FastReader(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 peek(){
		if (numChars == -1){
			return -1;
		}
		if (curChar >= numChars){
			curChar = 0;
			try{
				numChars = stream.read (buf);
			} catch (IOException e){
				return -1;
			}
			if (numChars <= 0){
				return -1;
			}
		}
		return buf[curChar];
	}

	public int nextInt(){
		int c = read ();
		while (isSpaceChar (c))
			c = read ();
		int sgn = 1;
		if (c == '-'){
			sgn = -1;
			c = read ();
		}
		int res = 0;
		do{
			if(c==','){
				c = read();
			}
			if (c < '0' || c > '9'){
				throw new InputMismatchException ();
			}
			res *= 10;
			res += c - '0';
			c = read ();
		} while (!isSpaceChar (c));
		return res * sgn;
	}

	public long nextLong(){
		int c = read ();
		while (isSpaceChar (c))
			c = read ();
		int sgn = 1;
		if (c == '-'){
			sgn = -1;
			c = read ();
		}
		long 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 nextString(){
		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 isWhitespace (c);
	}

	public static boolean isWhitespace(int c){
		return c == ' ' || c == '\n' || c == '\r' || c == '\t' || c == -1;
	}

	private String readLine0(){
		StringBuilder buf = new StringBuilder ();
		int c = read ();
		while (c != '\n' && c != -1){
			if (c != '\r'){
				buf.appendCodePoint (c);
			}
			c = read ();
		}
		return buf.toString ();
	}

	public String nextLine(){
		String s = readLine0 ();
		while (s.trim ().length () == 0)
			s = readLine0 ();
		return s;
	}

	public String nextLine(boolean ignoreEmptyLines){
		if (ignoreEmptyLines){
			return nextLine ();
		}else{
			return readLine0 ();
		}
	}

	public BigInteger nextBigInteger(){
		try{
			return new BigInteger (nextString ());
		} catch (NumberFormatException e){
			throw new InputMismatchException ();
		}
	}

	public char nextCharacter(){
		int c = read ();
		while (isSpaceChar (c))
			c = read ();
		return (char) c;
	}

	public double nextDouble(){
		int c = read ();
		while (isSpaceChar (c))
			c = read ();
		int sgn = 1;
		if (c == '-'){
			sgn = -1;
			c = read ();
		}
		double res = 0;
		while (!isSpaceChar (c) && c != '.'){
			if (c == 'e' || c == 'E'){
				return res * Math.pow (10, nextInt ());
			}
			if (c < '0' || c > '9'){
				throw new InputMismatchException ();
			}
			res *= 10;
			res += c - '0';
			c = read ();
		}
		if (c == '.'){
			c = read ();
			double m = 1;
			while (!isSpaceChar (c)){
				if (c == 'e' || c == 'E'){
					return res * Math.pow (10, nextInt ());
				}
				if (c < '0' || c > '9'){
					throw new InputMismatchException ();
				}
				m /= 10;
				res += (c - '0') * m;
				c = read ();
			}
		}
		return res * sgn;
	}

	public boolean isExhausted(){
		int value;
		while (isSpaceChar (value = peek ()) && value != -1)
			read ();
		return value == -1;
	}

	public String next(){
		return nextString ();
	}

	public SpaceCharFilter getFilter(){
		return filter;
	}

	public void setFilter(SpaceCharFilter filter){
		this.filter = filter;
	}

	public interface SpaceCharFilter{
		public boolean isSpaceChar(int ch);
	}
}
 /******************** Pair class ***********************/
 
 class Pair implements Comparable<Pair>{
 public long a;
 public long b;
 public Pair(){
  this.a = 0L;
  this.b = 0L;
 }
 public Pair(long a,long b){
  this.a = a;
  this.b = b;
 }
 public int compareTo(Pair p){
	if(this.a + this.b < p.a + p.b)return -1;
	else if(this.a + this.b > p.a + p.b )return 1;
	else return 0; 
 }
 public String toString(){
  return "a="+this.a+" b="+this.b;
 }
 
}