快速排序代码

Posted 2020-10-20 XJX

思路参考《算法导论》P95

这里有位老哥的文章写的挺形象的呀

http://developer.51cto.com/art/201403/430986.htm

我是参照书上实现的，觉得挺简单的

-------------------------------------------------------代码-------------------------------------------------------

 1 // QUICKSORT.cpp: 定义控制台应用程序的入口点。
 2 //
 3 
 4 #include "stdafx.h"
 5 #include <iostream>
 6 #include <random>
 7 
 8 using namespace std;
 9 
10 int PARTITION(int *A, int p, int r)
11 {
12     int x = A[r];
13     int i = p - 1;
14     int temp;
15     for (int j = p; j < r; j++)
16     {
17         if (A[j] <= x)
18         {
19             i++;
20             temp = A[i];
21             A[i] = A[j];
22             A[j] = temp;
23         }
24     }
25     temp = A[i+1];
26     A[i+1] = A[r];
27     A[r] = temp;
28     return i+1;
29 }
30 
31 int QUICKSORT(int *A,int p,int r)
32 {
33     if (p < r)
34     {
35         int q = PARTITION(A,p,r);
36         QUICKSORT(A, p, q - 1);
37         QUICKSORT(A, q + 1, r);
38     }
39     return 0;
40 }
41 
42 //------------------------------随机化版本--------------------------------
43 
44 int RANDOM_PARTITION(int *A, int p, int r)
45 {
46     uniform_int_distribution<unsigned> u(p,r);
47     default_random_engine e;
48     int i = u(e);//生成[p,r]之间的随机数
49     int temp = A[i];
50     A[i] = A[r];
51     A[r] = temp;
52     return PARTITION(A,p,r);
53 }
54 
55 int RANDOM_QUICKSORT(int *A, int p, int r)
56 {
57     if (p < r)
58     {
59         int q = RANDOM_PARTITION(A, p, r);
60         RANDOM_QUICKSORT(A, p, q - 1);
61         RANDOM_QUICKSORT(A, q + 1, r);
62     }
63     return 0;
64 }
65 
66 
67 int main()
68 {
69     int A[] = { 2,8,7,1,3,5,6,4 };
70     int B[] = { 2,8,7,1,3,5,6,4 };
71     for (auto c : A)
72         cout << c << ends;
73     cout << endl;
74 
75     QUICKSORT(A,0,7);
76     for (auto c : A)
77         cout << c << ends;
78     cout << endl;
79 
80     RANDOM_QUICKSORT(B, 0, 7);
81     for (auto c : B)
82         cout << c << ends;
83     cout << endl;
84     return 0;
85 }

运行结果：