根据《算法设计与分析基础》中对归并排序的描述，写了一分C#代码实现。
具体的实现代码如下：
1using System;
2using System.Collections.Generic;
3using System.Text;
4
5namespace MergeSort
6{
7 class Program
8 {
9 static void Main(string[] args)
10 {
11 Program p = new Program();
12
13 int[] a = new int[] { 4, 2, 1, 6, 3, 6, 0, -5, 1, 1 };
14
15 p.Sort(a);
16
17 for (int i = 0; i < a.Length; i++)
18 {
19 System.Console.WriteLine(a[i]);
20 }
21 }
22
23 /**//// <summary>
24 /// 利用归并排序按由下到大的顺序排序
25 /// </summary>
26 /// <param name="toBeSort"></param>
27 /// <returns></returns>
28 public int[] Sort(int[] toBeSort)
29 {
30 if (toBeSort.Length == 0)
31 {
32 throw new Exception("Sort array Error!");
33 }
34
35 if (toBeSort.Length > 1)
36 {
37 int[] part1 = Sort(get1Part(toBeSort));
38 int[] part2 = Sort(get2Part(toBeSort));
39
40 merger(part1, part2, toBeSort);
41 }
42
43 return toBeSort;
44 }
45
46 /**//// <summary>
47 /// 将part1和part2按照由小到大的顺序归并到数组toBeSort中
48 /// </summary>
49 /// <param name="part1"></param>
50 /// <param name="part2"></param>
51 /// <param name="toBeSort"></param>
52 private void merger(int[] part1, int[] part2, int[] toBeSort)
53 {
54 int index = 0;
55 int i1 = 0;
56 int i2 = 0;
57
58 while (i1 < part1.Length && i2 < part2.Length)
59 {
60 if (part1[i1] < part2[i2])
61 {
62 toBeSort[index] = part1[i1];
63 i1++;
64 }
65 else
66 {
67 toBeSort[index] = part2[i2];
68 i2++;
69 }
70
71 index++;
72 }
73
74 while (i1 < part1.Length)
75 {
76 toBeSort[index] = part1[i1];
77 index++;
78 i1++;
79 }
80
81 while (i2 < part2.Length)
82 {
83 toBeSort[index] = part2[i2];
84 index++;
85 i2++;
86 }
87 }
88
89 /**//// <summary>
90 /// Get the second part of the array.
91 /// </summary>
92 /// <param name="toBeSort">The array to be sort.</param>
93 /// <returns>The second part of the array.</returns>
94 private int[] get2Part(int[] toBeSort)
95 {
96 int len = toBeSort.Length - toBeSort.Length / 2;
97 int[] part2 = new int[len];
98
99 Array.Copy(toBeSort, toBeSort.Length / 2, part2, 0, len);
100
101 return part2;
102 }
103
104 /**//// <summary>
105 /// Get the first part of the array.
106 /// </summary>
107 /// <param name="toBeSort">The array to be sort.</param>
108 /// <returns>The first part of the array.</returns>
109 private int[] get1Part(int[] toBeSort)
110 {
111 int len = toBeSort.Length / 2;
112 int[] part1 = new int[len];
113
114 Array.Copy(toBeSort, part1, len);
115
116 return part1;
117 }
118 }
119}
120 对于分治法的效率分析，有一个通用的公示可以使用：通用分治递推公式。
