快速排序是一个递归算法，重点是Partition()函数的实现过程。随机快速排序中调用Randomized_Partition(),此函数的实现只需要在Partition()的基础上前面多一个随机化和交换的过程。
int Partition(int*A,int p,int r); int Randomized_Partition(int*A,int p,int r); void Quicksort(int *A,int p,int r); void Randomized_Quicksort(int*A,int p,int r); void Swap(int &a,int &b);
Quicksort.h
1 #include<iostream>
2 #include<time.h>
3 #include<stdio.h>
4 #include <stdlib.h>
5 #include<fstream>
6 using namespace std;
7
8 #include"Quicksort.h"
9
10 #define N 10000
11
12 int Num[N];
13 int choice;
14 double start,finish;
15
16 int main(void)
17 {
18
19 // Write N random numbers to data.txt
20 ofstream in;
21 in.open("data.txt",ios::trunc); //ios::trunc表示在打开文件前将文件清空,由于是写入,文件不存在则创建
22 int x;
23 srand((unsigned) time(NULL));
24 cout<<"Numbers needed to be sort are:"<<endl;
25 for(int n=0;n<N;n++)
26 {
27 x = rand() %100;
28 //cout<<x<<" ";
29 in<<x<<" ";
30 Num[n] = x;
31
32 }
33 cout<<endl;
34 in.close(); //勿忘关闭文件
35 /*
36 // Read data from data.txt
37 ifstream fin("data.txt");
38 vector<int> vec;
39
40 //fin Input value into idata,like cin>>a , cin get value from keyboard,fin get value from file
41 //This reading method won‘t get twice of the last data
42 int idata;
43 fin >> idata;
44 while (fin)
45 {
46 vec.push_back(idata);
47 fin >> idata;
48 }
49
50 //N = vec.size();
51 for(int i=0;i<N;i++)
52 {
53 Num[i]=vec[i];
54 }
55 */
56 cout<<"1: Quicksort Other: Randomized_Quick"<<endl<<"Your Choice: ";
57 cin>>choice;
58
59 //General Quicksort
60 start = clock();//
61 if(choice == 1)
62 {
63 Quicksort(Num,0,N-1);
64 finish = clock();//
65
66 //Output to screen & ResultData.txt
67 cout<<"Your Quciksort Result is:"<<endl;
68 in.open("ResultData.txt",ios::trunc);
69 for(int i=0;i<N;i++)
70 {
71 //cout<<Num[i]<<" ";
72 in<<Num[i]<<" ";
73 }
74 cout<<endl;
75 in.close();
76 cout<<"number of ticks in Quicksort is: "<<(finish-start)/CLOCKS_PER_SEC<<endl;//
77 return 0;
78 }
79
80 //Randomized_Quicksort
81 Randomized_Quicksort(Num,0,N-1);
82
83 finish = clock();//
84 //clock_t finish = clock();//
85
86 //Output to screen
87 cout<<"Your Randomized_Quciksort Result is:"<<endl;
88 in.open("ResultData.txt",ios::trunc);
89 for(int i=0;i<N;i++)
90 {
91 //cout<<Num[i]<<" ";
92 in<<Num[i]<<" ";
93 }
94 cout<<endl;
95 in.close();
96 /*
97 for(i=0;i<N;i++)
98 {
99 cout<<Num[i]<<" ";
100 }
101 cout<<endl;
102 */
103 cout<<"number of ticks in Randomized_Quicksort is: "<<(finish-start)/CLOCKS_PER_SEC<<endl;//
104 return 0;
105 }
main.cpp
1 #include"Quicksort.h"
2 int Partition(int*A,int p,int r)
3 {
4 int x = A[r];
5 int i = p-1;
6 for(int j=p;j<r;j++)
7 {
8 if(A[j]<=x)
9 {
10 i+=1;
11 if(i!=j)
12 {
13 Swap(A[i],A[j]);
14 }
15 }
16 }
17 Swap(A[i+1],A[r]);
18 return i+1;
19
20 }
Partition.cpp
1 #include"Quicksort.h"
2 void Quicksort(int *A,int p,int r)
3 {
4 if(p<r)
5 {
6 int q = Partition(A,p,r);
7 Quicksort(A,p,q-1);
8 Quicksort(A,q+1,r);
9 }
10 }
Quicksort.cpp
1 #include<time.h>
2 #include<stdlib.h>
3 #include"Quicksort.h"
4
5 int Randomized_Partition(int*A,int p,int r)
6 {
7 srand((unsigned) time(NULL));
8 int k = -1;
9 while(k<p)
10 {
11 k = rand() % (r+1);
12 }
13 Swap(A[k],A[r]);
14 //Partition(A,p,r);
15 int x = A[r];
16 int i = p-1;
17 for(int j=p;j<r;j++)
18 {
19 if(A[j]<=x)
20 {
21 i+=1;
22 if(i!=j)
23 {
24 Swap(A[i],A[j]);
25 }
26 }
27 }
28 Swap(A[i+1],A[r]);
29 return i+1;
30 }
Randomized_Partition.cpp
1 #include<iostream.h>
2 #include"Quicksort.h"
3 void Randomized_Quicksort(int *A,int p,int r)
4 {
5 if(p<r)
6 {
7 int q = Randomized_Partition(A,p,r);
8 Randomized_Quicksort(A,p,q-1);
9 Randomized_Quicksort(A,q+1,r);
10 }
11
12 }
Randomized_Quicksort.cpp
时间： 2024-10-06 19:54:16