快速排序-algorithms_3th

 1 #include <iostream>
 2 #include <random>
 3 using namespace std;
 4
 5 int PARTITION(int *const, const int &, const int &);
 6
 7 int rand_int(const int &up,const int &lo){
 8     random_device rd;
 9     mt19937 mt(rd());
10     uniform_int_distribution<> d(up,lo);
11     return d(mt);
12 }
13
14 void swap2(int &a, int &b){
15     int t = a;
16     a = b;
17     b = t;
18 }
19
20 void QUICK_SORT(int *const A, const int &p, const int &r){
21     if (p < r){
22         int q = PARTITION(A, p, r);
23         QUICK_SORT(A, p, q - 1);
24         QUICK_SORT(A, q + 1, r);
25     }
26 }
27
28 int PARTITION(int *const A, const int &p, const int &r){
29     /*通过随机选取中间元来进行均匀划分*/
30     int random_main = rand_int(p, r);
31     swap2(A[random_main], A[r]);
32     int x = A[r];
33     int i = p - 1;
34     for (int j = p; j < r;++j){
35         if (A[j] <= x){
36             ++i;
37             swap2(A[i], A[j]);
38         }
39     }
40     swap2(A[i + 1], A[r]);
41     return i + 1;
42 }
43
44 int main(void)
45 {
46     int a[] = { 2, 8, 7, 1, 3, 5, 6, 4 };
47     QUICK_SORT(a, 0, (end(a) - begin(a) - 1));
48     system("pause");
49     return 0;
50 }