Statistics

Problem Statement for "TheSumOfLuckyNumbers"

Problem Statement

John thinks 4 and 7 are lucky digits, and all other digits are not lucky. A lucky number is a number that contains only lucky digits in decimal notation.

Some numbers can be represented as a sum of only lucky numbers. Given an int n, return a int[] whose elements sum to exactly n. Each element of the int[] must be a lucky number. If there are multiple solutions, only consider those that contain the minimum possible number of elements, and return the one among those that comes earliest lexicographically. A int[] a1 comes before a int[] a2 lexicographically if a1 contains a smaller number at the first position where they differ. If n cannot be represented as a sum of lucky numbers, return an empty int[] instead.

Definition

Class:
TheSumOfLuckyNumbers
Method:
sum
Parameters:
int
Returns:
int[]
Method signature:
int[] sum(int n)
(be sure your method is public)

Constraints

  • n will be between 1 and 1,000,000, inclusive.

Examples

  1. 11

    Returns: {4, 7 }

    It is simple: 11 = 4 + 7.

  2. 12

    Returns: {4, 4, 4 }

    Now we need three summands to get 12.

  3. 13

    Returns: { }

    And now we can not get 13 at all.

  4. 100

    Returns: {4, 4, 4, 44, 44 }

  5. 1000000

    Returns: {4, 4, 44444, 477774, 477774 }

  6. 48

    Returns: {4, 44 }

  7. 1

    Returns: { }

  8. 57

    Returns: {4, 4, 7, 7, 7, 7, 7, 7, 7 }

  9. 25

    Returns: {4, 7, 7, 7 }

  10. 69

    Returns: {4, 4, 7, 7, 47 }

  11. 3603

    Returns: {444, 444, 444, 747, 747, 777 }

  12. 3456

    Returns: {444, 744, 744, 747, 777 }

  13. 3812

    Returns: {47, 747, 747, 747, 747, 777 }

  14. 3580

    Returns: {4, 474, 774, 774, 777, 777 }

  15. 3824

    Returns: {44, 744, 744, 744, 774, 774 }

  16. 957147

    Returns: {4, 4, 444, 4444, 474474, 477777 }

  17. 951000

    Returns: {444, 444, 444, 444, 474447, 474777 }

  18. 913356

    Returns: {74, 4474, 44477, 44777, 44777, 774777 }

  19. 971124

    Returns: {4, 44, 4444, 44444, 444444, 477744 }

  20. 998368

    Returns: {44, 44, 444, 4444, 44444, 474474, 474474 }

  21. 1

    Returns: { }

  22. 2

    Returns: { }

  23. 3

    Returns: { }

  24. 4

    Returns: {4 }

  25. 5

    Returns: { }

  26. 6

    Returns: { }

  27. 7

    Returns: {7 }

  28. 8

    Returns: {4, 4 }

  29. 9

    Returns: { }

  30. 10

    Returns: { }

  31. 17

    Returns: { }

  32. 18

    Returns: {4, 7, 7 }

  33. 19

    Returns: {4, 4, 4, 7 }

  34. 20

    Returns: {4, 4, 4, 4, 4 }

  35. 21

    Returns: {7, 7, 7 }

  36. 996199

    Returns: {4, 4, 44, 4474, 4474, 44474, 47474, 447474, 447777 }

  37. 744399

    Returns: {4, 4, 44, 474, 44774, 74774, 74774, 74774, 474777 }

  38. 774099

    Returns: {4, 4, 44, 474, 74474, 74774, 74774, 74774, 474777 }

  39. 774169

    Returns: {4, 4, 444, 444, 74474, 74474, 74774, 74774, 474777 }

  40. 774199

    Returns: {4, 4, 444, 474, 74474, 74474, 74774, 74774, 474777 }

  41. 813199

    Returns: {4, 4, 44, 4474, 4474, 4474, 4474, 47474, 747777 }

  42. 813499

    Returns: {4, 4, 44, 4474, 4474, 4474, 4474, 47774, 747777 }

  43. 813799

    Returns: {4, 4, 44, 4474, 4474, 4474, 4774, 47774, 747777 }

  44. 813829

    Returns: {4, 4, 74, 4474, 4474, 4474, 4774, 47774, 747777 }

  45. 813859

    Returns: {4, 444, 444, 4444, 4444, 4444, 4444, 47444, 747747 }

  46. 813869

    Returns: {4, 4, 444, 4444, 4474, 4474, 4474, 47774, 747777 }

  47. 813899

    Returns: {4, 4, 444, 4474, 4474, 4474, 4474, 47774, 747777 }

  48. 814099

    Returns: {4, 4, 44, 4474, 4474, 4774, 4774, 47774, 747777 }

  49. 814169

    Returns: {4, 4, 444, 4444, 4474, 4474, 4774, 47774, 747777 }

  50. 814199

    Returns: {4, 4, 444, 4474, 4474, 4474, 4774, 47774, 747777 }

  51. 814499

    Returns: {4, 4, 44, 74, 4474, 7474, 7474, 47474, 747477 }

  52. 816199

    Returns: {4, 4, 44, 4474, 4474, 4474, 7474, 47474, 747777 }

  53. 816499

    Returns: {4, 4, 44, 4474, 4474, 4474, 7474, 47774, 747777 }

  54. 816899

    Returns: {4, 4, 44, 44474, 74474, 74474, 74474, 74474, 474477 }

  55. 817199

    Returns: {4, 4, 44, 44474, 74474, 74474, 74474, 74474, 474777 }

  56. 817499

    Returns: {4, 4, 44, 74, 7474, 7474, 7474, 47474, 747477 }

  57. 993199

    Returns: {4, 4, 44, 4474, 4474, 44474, 44474, 447474, 447777 }

  58. 999997

    Returns: {44444, 44444, 44444, 44444, 44444, 777777 }

  59. 999962

    Returns: {44444, 477744, 477774 }

  60. 777776

    Returns: {74, 74, 74, 77, 777477 }

  61. 77863

    Returns: {4, 4, 4, 74, 77777 }

  62. 44444

    Returns: {44444 }

  63. 895

    Returns: {4, 444, 447 }

  64. 999999

    Returns: {4, 44444, 477774, 477777 }

  65. 984576

    Returns: {74, 44474, 44474, 447777, 447777 }

  66. 987654

    Returns: {44, 444, 44444, 47474, 447474, 447774 }

  67. 989564

    Returns: {444, 4444, 44444, 44744, 447744, 447744 }

  68. 999998

    Returns: {44444, 477777, 477777 }

  69. 999897

    Returns: {44, 44, 444, 44444, 477444, 477477 }

  70. 154841

    Returns: {44, 44, 44, 444, 4744, 74744, 74777 }

  71. 888888

    Returns: {444444, 444444 }

  72. 99991

    Returns: {4, 4, 4, 44, 4444, 47744, 47747 }

  73. 121

    Returns: {44, 77 }

  74. 959791

    Returns: {4, 4, 4, 444, 4444, 477444, 477447 }

  75. 78

    Returns: {4, 74 }

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