C++贪心算法实现活动安排问题

 1 #include <cstdio>
 2 #include <iostream>
 3 #include <ctime>
 4 #include <windows.h>
 5 #include <algorithm>
 6 #include <fstream>
 7 using namespace std;
 8 struct activity
 9 {
10     int no;
11     int start;
12     int finish;
13 };
14 bool cmp(const activity &x, const activity &y)
15 {
16     return x.finish<y.finish;//从小到大排<，若要从大到小排则>
17 }
18 int greedySelector(int m,int solution[],struct activity activity[]){
19     int number = 1;
20     solution[0] = 1;
21     int i,j = 0,counter = 1;
22     for(i = 1;i < m ;i++)
23     {
24         if(activity[i].start >=activity[j].finish)
25         {
26             solution[i] = 1;
27             j = i;
28             counter++;
29         }
30         else
31             solution[i] = 0;
32     }
33     cout << "The amount of activities is:"<<counter<<endl;
34     cout << "The solution is:";
35     for(i = 0 ;i < m ;i++)
36     {
37        if (solution[i] == 1)
38        {
39             cout << activity[i].no <<" ";
40        }
41     }
42     return counter;
43 }
44 int main(void)
45 {
46     LARGE_INTEGER nFreq;
47     LARGE_INTEGER nBeginTime;
48     LARGE_INTEGER nEndTime;
49     ofstream fout;
50     srand((unsigned int)time(NULL));
51     int m,i,j,t;
52     double cost;
53     cout << "Please enter the number of times you want to run the program:";
54     cin >> t;
55     fout.open("activity.txt",ios::app);
56     if(!fout){
57         cerr<<"Can not open file ‘activity.txt‘ "<<endl;
58         return -1;
59     }
60     fout.setf(ios_base::fixed,ios_base::floatfield);       //防止输出的数字使用科学计数法
61     for (j = 0;j < t;j++)
62     {
63         cout << "——————————————————The "<< j + 1 << "th test —————————————————"<<endl;
64         m = 1 + rand()%100000;
65         fout<<m<<",";
66         int solution[m];
67         activity activity[m];
68         for( i = 0;i < m;i++)
69         {
70             activity[i].no = i+1;
71             activity[i].start = 1 + rand()%1000;
72             while(1)
73             {
74                 activity[i].finish = 1 + rand()%10000;
75                 if(activity[i].finish > activity[i].start) break;
76             }
77         }
78         QueryPerformanceFrequency(&nFreq);
79         QueryPerformanceCounter(&nBeginTime);
80         sort(activity,activity+m,cmp);
81         greedySelector(m,solution,activity);
82         QueryPerformanceCounter(&nEndTime);
83         cost=(double)(nEndTime.QuadPart - nBeginTime.QuadPart) / (double)nFreq.QuadPart;
84         fout << cost << endl;
85         cout << "\nThe running time is:" << cost << " s" << endl;
86     }
87     fout.close();
88     cout << endl << endl;
89     cout << "Success!" << endl;
90     return 0;
91 }