//
//Description:0-1背包问题、背包问题（贪心算法）
//
#include <iostream>
#include <iomanip>
using namespace std;

typedef float Status;
typedef float Element;
int num;//物品个数
float c;//背包容量（即背包所能容纳的物品总重量）
static  float value(0);//当前背包中所有货品的总价值

class Object
{
public:
	int id;
	Element weight;
	Element price;
	Element avg_p;
	Element in_knapsack_Weight;//该物品已经放入背包中的重量

	void  avg_price()
	{
		avg_p = price / weight;
	}
};
Object obj[6];//对象数组  ???如何动态的为对象数组分配内存空间？？？
//目前可用物体数目为 5*******************

void input(int n)
{
	for (int i = 1; i <= n; i++)
	{
		cout << "\n请依次输入第" << i << "个物体的重量和价格" << endl;
		cin >> obj[i].weight >> obj[i].price;
		obj[i].id = i;
		obj[i].avg_price();
	}
	cout << endl;
}
void output(int n)
{
	for (int i = 1; i <= n; i++)
	{
		cout << "你所输入的第" << obj[i].id << "个物体的" << endl;
		cout << "重量\t价格\t单价" << endl;
		cout << obj[i].weight << "\t" << obj[i].price << "\t" << setprecision(4) << obj[i].avg_p;
		//setprecision(n)用于显示n位有效位数，使用时必须引用头文件 iomanip.h 
		cout << endl;
	}
}


//将单价由高到低进行排序
void compositor(int num)
{
	Object tem;

	for (int j = 1; j < num; j++)
	for (int i = 1; i <= num - j; i++)
	{

		if (obj[i].avg_p < obj[i + 1].avg_p)
		{
			tem = obj[i + 1];
			obj[i + 1] = obj[i];
			obj[i] = tem;
		}
	}
}
//往背包中放入物品,分为两种情况：
//情况1 ：（0-1背包算法）所指定种类的物品要么全放进去要么一点儿都不放进去；
//情况2 ：（背包算法）要么都可以放进去一部分或者全部.


//情况1执行代码：

void beibao_0_1(Status c, Status &value)
{
	value = 0;
	int i = 0;
	for ( i = 1; i <= num; i++)
	{
		if (obj[i].weight > c)
			continue;
		else
		{
			obj[i].in_knapsack_Weight = obj[i].weight;
			value += obj[i].weight*obj[i].avg_p;
			c -= obj[i].weight;
		}
	}


	cout << "\n放入了背包中的物品情况如下\n";
	for (i = 1; i <= num; i++)
	{
		if (obj[i].in_knapsack_Weight > 0)
		{
			cout << "\t物品" << obj[i].id << "放入的重量为 " << obj[i].in_knapsack_Weight << " ,其价值为 " << obj[i].price << endl;
		}
	}
}

//情况2执行代码：
void beibao(Status c, Status &value)
{
	value = 0;
	int i = 0;
	for (i = 1; i <= num; i++)
	{
		if (obj[i].weight >= c)
		{
			obj[i].in_knapsack_Weight = c;
			value += c*obj[i].avg_p;
			break;
		}
		else
		{
			obj[i].in_knapsack_Weight = obj[i].weight;
			value += obj[i].weight*obj[i].avg_p;
			c -= obj[i].weight;
		}
	}


	cout << "\n放入了背包中的物品情况如下\n";
	for (i = 1; i <= num; i++)
	{
		if (obj[i].in_knapsack_Weight > 0)
		{
			Status z;
			z = obj[i].in_knapsack_Weight*obj[i].avg_p;
			cout << "\t物品" << obj[i].id << "放入的重量为 " << obj[i].in_knapsack_Weight << " ,其价值为 " << z << endl;
		}
	}
}

void chose_operator()
{
loop:
	cout << "\n\t=========请选择一种算法============" << endl;
	cout << "   1----- 0-1 背包算法   2-----背包算法   3(或者其他键)------Exit " << endl;
	int n;
	cin >> n;
	switch (n)
	{
	case 1: 
	      {//0-1背包算法
			loop2:   cout << "\n=====0-1背包算法===== ";
				beibao_0_1(c, value);
				cout << "背包容量为 " << c << " ,背包内的物品总价值为 " << value << " 元\n\n";
				cout << "想看一下另一种算法吗？（Y/N）\n";
				char z;
				cin >> z;

				if (z - 'Y' == 0 || z - 'Y' == 32)
				{
					goto loop1;
				}
				else
				if (z - 'N' != 0 || z - 'n' != 32)
				{
					cout << "您的输入有误！" << endl;
				}
	      }; break;
	case 2: 
	      {//背包算法
		  loop1:    
			    cout << "\n=====背包算法===== ";
				beibao(c, value);
				cout << "背包容量为 " << c << " ,背包内的物品总价值为 " << value << " 元\n";

				cout << "想看一下另一种算法吗？（Y/N）\n";
				char z;
				cin >> z;

				if (z - 'Y' == 0)
				{
					goto loop2;
				}
				else
				if (z - 'N' != 0)
				{
					cout << "您的输入有误！,程序退出！" << endl;
				}
			}; break;
	case 3: break;
	default:
	       {
			   cout << "输入有误，请重试！\n";
			   goto loop;
	        }

	}
}
 
void main()
{
 	cout << "\n\t============贪心算法－背包问题============" << endl;
	cout << "  请输入物品个数" << endl;
	cin >> num;

	input(num);
	output(num);
	compositor(num);
	cout << "\n----------排序后：" << endl;
	output(num);

	cout << "\n   请输入背包的容量（kg）\n";
	cin >> c;

	chose_operator();
}