Binary search, binarysearch

Binary search, binarysearch

1. // Configure //--------------------------------------------------------------------------------------------------------------------
2. // <Copyright company = "Chimomo's Company" file = "Program. cs">
3. // Respect the work.
4. // </Copyright>
5. // <Summary>
6. // The binary search (not recursive ).
7. // [Prerequisites for searching in half]:
8. // 1. The sequence to be searched must adopt a sequential storage structure.
9. // 2. The sequence to be searched must be ordered by the keyword size.
10. /// </Summary>
11. // Configure //--------------------------------------------------------------------------------------------------------------------
13. Namespace CSharpLearning
14. {
15. Using System;
17. /// <Summary>
18. /// The program.
19. /// </Summary>
20. Internal class Program
21. {
22. /// <Summary>
23. /// Entry point into console application.
24. /// </Summary>
25. Public static void Main ()
26. {
27. Int [] a = {1, 2, 3, 4, 5, 6, 7, 8, 9 };
28. Console. WriteLine (BinarySearch (a, 6, 9 ));
29. }
31. /// <Summary>
32. /// Search for elements whose values are key (non-recursive search) in an ordered array a with a length of n ).
33. /// </Summary>
34. /// <Param name = "a">
35. /// The array to be searched.
36. /// </Param>
37. /// <Param name = "key">
38. /// Target element.
39. /// </Param>
40. /// <Param name = "n">
41. /// Array length.
42. /// </Param>
43. /// <Returns>
44. /// If the target element is found, the subscript of the target element in the array is returned; otherwise,-1 is returned.
45. /// </Returns>
46. Private static int BinarySearch (int [] a, int key, int n)
47. {
48. Int low = 0;
49. Int high = n-1;
50. While (low <= high)
51. {
52. Int mid = (low + high)/2;
53. If (a [mid] = key)
54. {
55. Return mid;
56. }
58. If (a [mid] <key)
59. {
60. Low = mid + 1;
61. }
62. Else
63. {
64. High = mid-1;
65. }
66. }
68. Return-1;
69. }
70. }
71. }
73. // Output:
74. /*
75. 5
76. */
77. Time Complexity: O (log_2n)