01背包回溯

backtrack_SubsetTree(t+1);//搜索左子树
}
if(FrontProcessValue(t-1) + Bound(t+1)> MaxValue)//剪枝函数
{//在一定剩余重量情况下剩下物品能够得到的最大价值比maxvalue要大
IsSelected[t]=false;
{
if(t == products.length)//到达叶节点
{
System.out.println("到达叶节点 ");
int tempvalue = 0;
int tempweight = 0;
for(int j=0;j<products.length;j++)
class Product {
public int No;
public int Weight;
public int Value;
public Product(int no,int weight,int value){
No = no;
Weight = weight;
backtrack_SubsetTree(t+1);//搜索右子树
}
}
}
private static int Bound(int i) {//在一定剩余重量情况下剩下物品能够得到的最大价值
//贪心算法 求更准确的上界
int temp = 0;
static boolean IsSelected[] = new boolean[products.length];
static int MaxWeight = 50;
static inቤተ መጻሕፍቲ ባይዱ MaxValue = 0;//整体最优解
static void backtrack_SubsetTree(int t)
if(IsSelected[j])
{
tempvalue += products[j].Value;
tempweight += products[j].Weight;
}
if(tempweight <= MaxWeight && tempvalue > MaxValue)
//java List 排序 Collections.sort() 对 List 排序
import parator;
import java.util.List;
import java.util.ArrayList;
import java.util.Collections;
int temp = 0;
for(int j=0;j<=t;j++)
if(IsSelected[j])
{
temp += products[j].Value;
}
return temp;
}
public static void main(String[] args) {
backtrack_SubsetTree(0);
System.out.println("最优解:"+MaxValue);
}
}
for(int j=i;j<products.length;j++)
temp += products[j].Value;
return temp;
}
private static int FrontProcessWeight(int t) {
int temp = 0;
Value = value;
}
}
public class KnapTest {
static Product products[] = new Product[]{new Product(1,10,60),new Product(2,20,100),new Product(3,30,120)};
for(int j=0;j<=t;j++)
if(IsSelected[j])
{
temp += products[j].Weight;
}
return temp;
}
private static int FrontProcessValue(int t) {
MaxValue = tempvalue;
return;
}
else
{
if(FrontProcessWeight(t-1)+products[t].Weight <= MaxWeight)//剪枝函数
{//剩余重量能够放得下第t个物品
IsSelected[t]=true;