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  1. import java.util.ArrayList;
  2.  
  3. class CombinationOf3And4 {
  4.  
  5. /*
  6.  * http://w...content-available-to-author-only...s.org/zoho-interview-set-2-campus/
  7.  * Form a number system with only 3 and 4. Find the nth number of the number system.
  8.  * e.g. The numbers are: 3, 4, 33, 34, 43, 44, 333, 334, 343, 344, 433, 434, 443, 444, 3333, 3334, 3343, 3344, 3433, 3434, 3443, 3444 ….
  9.  */
  10. 	public static void main(String[] args) {
  11. 		printCombinations(20);
  12. 	}
  13. 	public static void printCombinations(int n){
  14. 		ArrayList<String> numbers = new ArrayList<String> ();
  15. 		numbers.add("3");
  16. 		numbers.add("4");
  17. 		int currentNumber = 0;
  18. 		while(numbers.size()<n){
  19. 			ArrayList<String> threePrefixed = new ArrayList<String>();
  20. 			ArrayList<String> fourPrefixed = new ArrayList<String>();
  21.  
  22. 			for(int i=currentNumber;i<numbers.size();i++){
  23. 				// Retrieve all numbers.
  24. 				// For every number create new number with prefix "3"  & with prefix "4".
  25. 				// then push all 3-prefixed-number into array and then 4-prefixed-number 
  26. 				threePrefixed.add("3"+numbers.get(i));
  27. 				fourPrefixed.add("4"+numbers.get(i));
  28. 				currentNumber++;
  29. 			}
  30.  
  31. 			for(String s:threePrefixed){
  32. 				numbers.add(s);
  33. 			}
  34. 			for(String s:fourPrefixed){
  35. 				numbers.add(s);
  36. 			}
  37. 		}
  38. 		System.out.println("Printing result");
  39. 		for(String s:numbers){
  40. 			System.out.print(" "+s);
  41. 		}
  42.  
  43. 	}
  44. }
  45.  
  46.  
Success #stdin #stdout 0.08s 380224KB
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Standard input is empty
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Printing result
 3 4 33 34 43 44 333 334 343 344 433 434 443 444 3333 3334 3343 3344 3433 3434 3443 3444 4333 4334 4343 4344 4433 4434 4443 4444
https://ideone.com/nkuJkT
language:
Java (HotSpot 12)
created:
10 years ago
visibility:
public

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