ustbfym 2019-11-04
_(:з」∠)_
#include <cstdio>
#include <iostream>
#include <ctime>
#include <windows.h>
#include <algorithm>
#include <fstream>
using namespace std;
struct object
{
int no;
double weight;
double value;
double average;
};
bool cmp(const object &x, const object &y)
{
return x.average > y.average;//从小到大排<,若要从大到小排则>
}
void greedySelector(int m,int W,int solution[],struct object object[]){
int i = 0,V = 0,j = 0;
while(object[i].weight < W)
{
solution[i] = 1;
W = W - object[i].weight;
V = V + object[i].value;
i++;
}
V = V + (W/object[i].weight)*object[i].value;
solution[i] = 1;
cout << "The corresponding value of the optimal option is:" << V << endl;
/*for( i = 0; i < m; i++)
{
if(solution[i] == 1)
{
cout << object[i].no << endl;
}
}*/
}
int main(void)
{
LARGE_INTEGER nFreq;
LARGE_INTEGER nBeginTime;
LARGE_INTEGER nEndTime;
ofstream fout1;
ofstream fout2;
srand((unsigned int)time(NULL));
int m,i,j,t;
double W;
double cost;
cout << "Please enter the number of times you want to run the program:";
cin >> t;
fout1.open("backpack-object.txt",ios::app);
if(!fout1){
cerr<<"Can not open file ‘backpack-object.txt‘ "<<endl;
return -1;
}
fout1.setf(ios_base::fixed,ios_base::floatfield); //防止输出的数字使用科学计数法
fout2.open("backpack-weight.txt",ios::app);
if(!fout2){
cerr<<"Can not open file ‘backpack-weight.txt‘ "<<endl;
return -1;
}
fout2.setf(ios_base::fixed,ios_base::floatfield); //防止输出的数字使用科学计数法
for (j = 0;j < t;j++)
{
cout << "——————————————————The "<< j + 1 << "th test —————————————————"<<endl;
m = 1 + rand()%100000; //物品个数
W = 10 + rand()%100000; //背包总重量
fout1 << m << ",";
fout2 << (int)W << ",";
int solution[m];
object object[m];
for( i = 0;i < m;i++)
{
object[i].no = i + 1;
object[i].value = 1 + rand()%10000;
object[i].weight = 1 + rand()%10000;
object[i].average = object[i].value/object[i].weight;
}
QueryPerformanceFrequency(&nFreq);
QueryPerformanceCounter(&nBeginTime);
sort(object,object + m,cmp);
greedySelector(m,W,solution,object);
QueryPerformanceCounter(&nEndTime);
cost=(double)(nEndTime.QuadPart - nBeginTime.QuadPart) / (double)nFreq.QuadPart;
fout1 << cost << endl;
fout2 << cost << endl;
cout << "The running time is:" << cost << " s" << endl;
}
fout1.close();
fout2.close();
cout << endl;
cout << "Success!" << endl;
return 0;
}