算法学习之基础(背包 列队 栈) 习题1.3.34随机背包的实现

背包的API

void add()

int size()

boolean isEmpty()

背包的遍历用Iterator

代码、

package gh;

import java.util.Iterator;
/**
 * 随机背包
 * @author ganhang
 *
 * @param <T>
 */
public class RandomBag<T>implements Iterable<T> {
    private int n;//元素数量
    private T [] bag;
    public RandomBag(int max){
        bag=(T[])new Object[max];
    }
    public boolean isEmpty(){
        return n==0;
    }
    
    public int size(){
        return n;
    }
    public void add(T item){
        bag[n++]=item;
    }

    @Override
    public Iterator<T> iterator() {
        // TODO Auto-generated method stub
        return new RandomBagIterator();
    }
    private class RandomBagIterator implements Iterator<T>{
        public RandomBagIterator(){
            shuffle(bag);//构造函数中随机排列下数组中的元素
        }
        private void shuffle(T b[]){//数组的随机排序
            int N=b.length;
            for(int i=0;i<N;i++){
                int r=i+(int)(Math.random()*(N-i));
                T temp=b[i];
                b[i]=b[r];
                b[r]=temp;
            }
        }
        @Override
        public boolean hasNext() {
            // TODO Auto-generated method stub
            return n!=0;
        }

        @Override
        public T next() {
            // TODO Auto-generated method stub
            return bag[--n];
        }

        @Override
        public void remove() {
            // TODO Auto-generated method stub
            
        }
        
    }
    
}