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  1. import java.util.*;
  2. import java.lang.*;
  3. import java.io.*;
  4.  
  5. /* Name of the class has to be "Main" only if the class is public. */
  6. class Ideone
  7. {
  8. 	public static void main (String[] args) throws java.lang.Exception
  9. 	{
  10.  
  11. 		// Main array to be accessed from innermost to outermost element
  12. 		int[] arr = new int[]{1,2,3,4,5};
  13. 		int[] map = creatIndexMap(arr.length);
  14.         printOut(arr, map);
  15.  
  16.         int[] arr2 = new int[]{1,2,3,4,5,6};
  17. 		int[] map2 = creatIndexMap(arr2.length);
  18.         printOut(arr2, map2);
  19. 	}
  20.  
  21. 	public static int[] creatIndexMap(int length) {
  22.  
  23. 		// Create a deque so elements can be removed from both ends
  24. 		Deque<Integer> tmp = new LinkedList<Integer>();
  25. 		for(int i = 0; i < length; i++) {
  26. 			tmp.add(i);
  27. 		}
  28.  
  29. 		// In alternation remove the last and first entries of tmp
  30. 		// and add them in reverse order to map array
  31. 		int[] map = new int[length];
  32. 		int index = length-1;
  33. 		while (!tmp.isEmpty()) {
  34. 			// Remove last element
  35. 			map[index--] = (int) tmp.removeLast();
  36.  
  37. 			// Remove first element
  38. 			if(!tmp.isEmpty()) {
  39. 				map[index--] = (int) tmp.removeFirst();
  40. 			}
  41. 		}
  42. 		return map;
  43. 	}
  44.  
  45. 	// Dispay results
  46. 	public static void printOut(int[] arr, int[] map) {
  47. 		System.out.println("Original array:");
  48. 		for(int i = 0; i < arr.length; i++) {
  49. 			System.out.print( arr[i] + " ");
  50. 		}
  51.  
  52. 		System.out.println();
  53. 		System.out.println("Index-mapped array:");
  54. 		for(int i = 0; i < arr.length; i++) {
  55. 			System.out.print( arr[map[i]] + " ");
  56. 		}
  57. 		System.out.println();
  58. 	}
  59. }
Success #stdin #stdout 0.1s 320256KB
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Standard input is empty
stdout
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Original array:
1 2 3 4 5 
Index-mapped array:
3 2 4 1 5 
Original array:
1 2 3 4 5 6 
Index-mapped array:
3 4 2 5 1 6
https://ideone.com/SneAAo
language:
Java (HotSpot 12)
created:
8 years ago
visibility:
public

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