C++贪心算法实现活动安排问题
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2022-05-31 19:18:09
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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 }