qq_33312212 于 2016.03.20 18:32 提问

ACM菜鸟新手 DP多重背包问题 求大神解答
`````` #include<iostream>
#include <cstring>
using namespace std;

int n[7];  //价值为i的物品的个数
int v;  //背包容量
int SumValue;  //物品总价值
bool flag;    //标记是否能平分SumValue
int dp[100000];  //状态数组

int max(int a,int b)
{
return a>b?a:b;
}

/*完全背包*/
void CompletePack(int cost,int weight)
{
for(int i=cost;i<=v;i++)
{
dp[i]=max(dp[i],dp[i-cost]+weight);
if(dp[i]==v)    //剪枝，当能够平分SumValue时退出
{
flag=true;
return;
}
}

return;
}

/*01背包*/
void ZeroOnePack(int cost,int weight)
{
for(int i=v;i>=cost;i--)
{
dp[i]=max(dp[i],dp[i-cost]+weight);
if(dp[i]==v)    //剪枝
{
flag=true;
return;
}
}
return;
}

/*多重背包*/
void MultiplePack(int cost,int weight,int amount)
{
if(cost*amount>=v)
{
CompletePack(cost,weight);
return;
}

if(flag)    //剪枝
return;

/*二进制优化*/
int k=1;
while(k<amount)
{
ZeroOnePack(k*cost,k*weight);

if(flag)    //剪枝
return;

amount-=k;
k*=2;
}
ZeroOnePack(amount*cost,amount*weight);

return;
}

int main(int i)
{
int test=1;
while(cin>>n[1]>>n[2]>>n[3]>>n[4]>>n[5]>>n[6])
{
SumValue=0;  //物品总价值

for(i=1;i<=6;i++)
SumValue+=i*n[i];

if(SumValue==0)
break;

if(SumValue%2)    //sum为奇数，无法平分
{
cout<<"Collection #"<<test++<<':'<<endl;
cout<<"Can't be divided."<<endl<<endl;    //注意有空行
continue;
}

v=SumValue/2;
memset(dp,-1,sizeof(dp));
dp[0]=0;
flag=false;

for(i=1;i<=6;i++)
{
MultiplePack(i,i,n[i]);

if(flag)    //剪枝
break;
}

if(flag)
{
cout<<"Collection #"<<test++<<':'<<endl;
cout<<"Can be divided."<<endl<<endl;             continue;
}
else
{
cout<<"Collection #"<<test++<<':'<<endl;
cout<<"Can't be divided."<<endl<<endl;
continue;
}
}
return 0;
}
``````

`````` void MultiplePack(int cost,int weight,int amount)
{
if(cost*amount>=v)
{
CompletePack(cost,weight);
return;
}

if(flag)    //剪枝
return;

/*二进制优化*/
``````