add

Author: AlbertKidd

Chapter1_Fundamentals/c1_3_bags_queues_stacks/RandomBag.java

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+package c1_3_bags_queues_stacks;
+
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+import java.util.Random;
+
+public class RandomBag<Item> implements Iterable<Item> {
+	
+	private int N;
+	private Item[] bag;
+	
+	public RandomBag(){
+		N = 0;
+		bag = (Item[]) new Object[1];
+	}
+	
+	public boolean isEmpty(){
+		return N == 0;
+	}
+	
+	public int size(){
+		return N;
+	}
+	
+	public void add(Item item){
+		if(N == bag.length)
+			resize(2 * bag.length);
+		bag[N++] = item;
+	}
+	
+	private void resize(int n){
+		assert n >= N;
+		Item[] temp = (Item[]) new Object[n];
+		for(int i = 0; i < N; i++)
+			temp[i] = bag[i];
+		bag = temp;
+	}
+
+	@Override
+	public Iterator<Item> iterator() {
+		// TODO Auto-generated method stub
+		return new ListIterator();
+	}
+	
+	private class ListIterator implements Iterator<Item> {
+
+		private int num;
+		
+		public ListIterator(){
+			randomSort();
+		}
+		
+		private Random rand = new Random();
+		private void randomSort(){
+			for(int i = 0; i < N; i++){
+				int randomIndex = i + rand.nextInt(N - i);
+				Item item = bag[i];
+				bag[i] = bag[randomIndex];
+				bag[randomIndex] = item;
+			}
+		}
+		
+		@Override
+		public boolean hasNext() {
+			return num < N;
+		}
+
+		@Override
+		public Item next() {
+			if(!hasNext())
+				throw new NoSuchElementException();
+			return bag[num++];
+		}
+		
+	}
+}