#include <iostream.h>
struct goodinfo
{
float p; //物品效益
float w; //物品重量
float X; //物品该放的数量
int flag; //物品编号
};//物品信息结构体
void Insertionsort(goodinfo goods[],int n)
{//插入排序，按pi/wi价值收益进行排序，一般教材上按冒泡排序
int j,i;
for(j=2;j<=n;j++)
{
goods[0]=goods[j];
i=j-1;
while (goods[0].p>goods[i].p)
{
goods[i+1]=goods[i];
i--;
}
goods[i+1]=goods[0];
}
}//按物品效益，重量比值做升序排列
void bag(goodinfo goods[],float M,int n)
{
float cu;
int i,j;
for(i=1;i<=n;i++)
goods[i].X=0;
cu=M; //背包剩余容量
for(i=1;i<n;i++)
{
if(goods[i].w>cu)//当该物品重量大与剩余容量跳出
break;
goods[i].X=1;
cu=cu-goods[i].w;//确定背包新的剩余容量
}
if(i<=n)
goods[i].X=cu/goods[i].w;//该物品所要放的量
/*按物品编号做降序排列*/
for(j=2;j<=n;j++)
{
goods[0]=goods[j];
i=j-1;
while (goods[0].flag<goods[i].flag)
{
goods[i+1]=goods[i];
i--;
}
goods[i+1]=goods[0];
}
///
cout<<"最优解为:"<<endl;
for(i=1;i<=n;i++)
{
cout<<"第"<<i<<"件物品要放:";
cout<<goods[i].X<<endl;
}
}
void main()
{
cout<<"|--------运用贪心法解背包问题---------|"<<endl;
int j,n; float M;
goodinfo *goods;//定义一个指针
while(j)
{
cout<<"请输入物品的总数量：";
cin>>n;
goods=new struct goodinfo [n+1];//
cout<<"请输入背包的最大容量：";
cin>>M;
cout<<endl;
int i;
for(i=1;i<=n;i++)
{ goods[i].flag=i;
cout<<"请输入第"<<i<<"件物品的重量:";
cin>>goods[i].w;
cout<<"请输入第"<<i<<"件物品的效益:";
cin>>goods[i].p;
goods[i].p=goods[i].p/goods[i].w;//得出物品的效益，重量比
cout<<endl;
}
Insertionsort(goods,n);
bag(goods,M,n);
cout<<"press <1> to run agian"<<endl;
cout<<"press <0> to exit"<<endl;
cin>>j;
}
}
