Java实现Stack、Queue、BinaryTree

最新推荐文章于 2024-08-16 09:05:29 发布

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本文通过具体实例介绍了如何使用Java实现三种基本的数据结构：栈、队列和二叉树。包括使用数组实现栈的基本操作如压栈、弹栈及查看栈顶元素；使用数组实现队列的插入、删除及查看队首元素；递归实现二叉树的插入及遍历等。

1、用数组实现Stack：

public class MyStack {
	private int maxSize;
	private Integer[] array;
	private int top;

	public MyStack(int maxSize) {
		this.maxSize = maxSize;
		this.array = new Integer[maxSize];
		this.top = -1;
	}

	public void push(int item) {
		if (isFull()) {
			System.out.println("Stack is full");
		} else {
			array[++top] = item;
		}
	}

	public Integer peek() {
		if (isEmpty()) {
			System.out.println("Stack is empty");
			return null;
		} else {
			return array[top];
		}
	}

	public Integer pop() {
		if (isEmpty()) {
			System.out.println("Stack is empty");
			return null;
		} else {
			return array[top--];
		}
	}

	public boolean isEmpty() {
		return top == -1;
	}

	public boolean isFull() {
		return top == maxSize - 1;
	}

	public static void main(String[] args) {
		MyStack myStack = new MyStack(10);
		myStack.push(1);
		myStack.push(3);
		System.out.println("peek: " + myStack.peek());
		myStack.push(5);
		System.out.println("pop: " + myStack.pop());
		System.out.println("peek: " + myStack.peek());
		myStack.push(6);
		System.out.println("peek: " + myStack.peek());
		System.out.println("pop: " + myStack.pop());
		System.out.println("pop: " + myStack.pop());
		System.out.println("pop: " + myStack.pop());
		System.out.println("pop: " + myStack.pop());
	}
}

2、用数组实现Queue：

public class MyQueue {
	private int maxSize;
	private Integer[] array;
	private int front;
	private int rear;
	private int itemCount;

	public MyQueue(int maxSize) {
		this.maxSize = maxSize;
		this.array = new Integer[maxSize];
		this.front = 0;
		this.rear = -1;
		this.itemCount = 0;
	}

	public void insert(int item) {
		if (isFull()) {
			System.out.println("Queue is full");
		} else {
			if (rear == maxSize - 1) {
				rear = -1;
			}
			array[++rear] = item;
			itemCount++;
		}
	}

	public Integer remove() {
		if (isEmpty()) {
			System.out.println("Queue is empty");
			return null;
		} else {
			int temp = array[front++];
			if (front == maxSize) {
				front = 0;
			}
			itemCount--;
			return temp;
		}
	}

	public Integer peek() {
		if (isEmpty()) {
			System.out.println("Queue is empty");
			return null;
		} else {
			return array[front];
		}
	}

	public boolean isEmpty() {
		return itemCount == 0;
	}

	public boolean isFull() {
		return itemCount == maxSize;
	}

	public static void main(String[] args) {
		MyQueue myQueue = new MyQueue(5);
		myQueue.insert(1);
		myQueue.insert(2);
		myQueue.insert(3);
		myQueue.insert(4);
		myQueue.insert(5);
		myQueue.insert(6);
		System.out.println("peek: " + myQueue.peek());
		myQueue.insert(5);
		System.out.println("remove: " + myQueue.remove());
		System.out.println("peek: " + myQueue.peek());
		myQueue.insert(6);
		System.out.println("peek: " + myQueue.peek());
		System.out.println("remove: " + myQueue.remove());
		System.out.println("remove: " + myQueue.remove());
		System.out.println("peek: " + myQueue.peek());
		System.out.println("remove: " + myQueue.remove());
		System.out.println("remove: " + myQueue.remove());
	}
}

3、递归实现BinaryTree：

public class MyBinaryTree {

	private static class Node {
		int data;
		Node left;
		Node right;

		public Node(int data) {
			this.data = data;
			this.left = null;
			this.right = null;
		}
	}

	public Node root;

	public MyBinaryTree() {
		root = null;
	}

	private Node insert(Node node, int data) {
		if (node == null) {
			node = new Node(data);
		} else {
			if (data <= node.data) {
				node.left = insert(node.left, data);
			} else {
				node.right = insert(node.right, data);
			}
		}
		return node;
	}

	public void insert(int data) {
		root = insert(root, data);
	}

	public void insert(int[] data) {
		for (int i : data) {
			insert(i);
		}
	}

	public void preOrder(Node node) {
		if (node == null) {
			return;
		}
		System.out.println(node.data);
		preOrder(node.left);
		preOrder(node.right);
	}

	public void inOrder(Node node) {
		if (node == null) {
			return;
		}
		preOrder(node.left);
		System.out.println(node.data);
		preOrder(node.right);
	}

	public void postOrder(Node node) {
		if (node == null) {
			return;
		}
		preOrder(node.left);
		preOrder(node.right);
		System.out.println(node.data);
	}

	public static void main(String[] args) {
		MyBinaryTree binaryTree = new MyBinaryTree();
		int[] data = { 4, 8, 7, 2, 9, 3, 1, 6, 5 };
		binaryTree.insert(data);
		System.out.println("preOrder:");
		binaryTree.preOrder(binaryTree.root);
		System.out.println("inOrder:");
		binaryTree.inOrder(binaryTree.root);
		System.out.println("postOrder:");
		binaryTree.postOrder(binaryTree.root);
	}
}