二叉搜索树的非递归与递归遍历以及层次遍历

二叉搜索树的递归遍历

public class BinaryTree {
	public int value;
	public BinaryTree left;
	public BinaryTree right;

	public void store(int value) {
		if (value < this.value) {
			if (left == null) {
				left = new BinaryTree();
				left.value = value;
			} else {
				left.store(value);
			}
		} else if (value > this.value) {
			if (right == null) {
				right = new BinaryTree();
				right.value = value;
			} else {
				right.store(value);
			}
		}
	}
	public boolean find(int value) {
		System.out.println("happen" + this.value);
		if (value == this.value) {
			return true;
		} else if (value > this.value) {
			if (right == null)
				return false;
			return right.find(value);
		} else {
			if (left == null)
				return false;
			return left.find(value);
		}
	}
	public void preList() {
		System.out.print(this.value + ",");
		if (left != null)
			left.preList();
		if (right != null)
			right.preList();
	}
	public void middleList() {
		if (left != null)
			left.middleList();
		System.out.print(this.value + ",");
		if (right != null)
			right.middleList();
	}

	public void afterList() {
		if (left != null)
			left.afterList();
		if (right != null)
			right.afterList();
		System.out.print(this.value + ",");
	}

	public static void main(String[] args) {
		/*
		 * int[] data = new int[20]; for (int i = 0; i < data.length; i++) { data[i] = (int) (Math.random() * 100) + 1;
		 * System.out.print(data[i] + ","); }
		 */
		int[] data = { 7, 5, 8, 3, 6, 4, 9 };
		System.out.println();

		BinaryTree root = new BinaryTree();
		root.value = data[0];
		for (int i = 1; i < data.length; i++) {
			root.store(data[i]);
		}

		// root.find(data[19]);
		System.out.println("前序遍历");
		root.preList();
		System.out.println();
		System.out.println("中序遍历");
		root.middleList();
		System.out.println();
		System.out.println("后续遍历");
		root.afterList();
	}
}

非递归遍历方式可以采用栈来实现

// 先序遍历（非递归）---借助于栈实现
public void nrPreOrderTraverse() {
	Stack<Node<T>> stack = new Stack<Node<T>>();
	Node<T> node = root;
	stack.push(node);
	while (!stack.isEmpty()) {
		node = stack.pop();
		System.out.println(node.getValue());
		// 右子节点先入栈
		if (node.getRight() != null)
			stack.push(node.getRight());
		if (node.getLeft() != null)
			stack.push(node.getLeft());
	}
}
// 中序遍历(非递归)----借助于栈实现
public void nrInOrderTraverse() {
	Stack<Node<T>> stack = new Stack<Node<T>>();
	Node<T> node = root;
	while (node != null || !stack.isEmpty()) {
		if (node != null) {
			stack.push(node);
			node = node.getLeft();
		} else {
			node = stack.pop();
			System.out.print(node.getValue() + " ");
			node = node.getRight();
		}
	}
}
// 后续遍历(非递归)
public void nrPostOrderTraverse() {
	Stack<Node<T>> stack = new Stack<Node<T>>();
	Node<T> node = root;
	Node<T> preNode = null;// 表示最近一次访问的节点
	while (node != null || !stack.isEmpty()) {
		while (node != null) {
			stack.push(node);
			node = node.getLeft();
		}
		node = stack.peek();
		if (node.getRight() == null || node.getRight() == preNode) {
			System.out.println(node.getValue());
			node = stack.pop();
			preNode = node;
			node = null;
		} else {
			node = node.getRight();
		}
	}
}
// 后续遍历(非递归)----借助于两个栈实现
public void nrPostOrder() {
	LinkedList<Node<T>> stack1 = new LinkedList<>(), stack2 = new      LinkedList<>();
	stack1.push(root);
        while (!stack1.isEmpty()) {
		Node<T> node = stack1.pop();
		stack2.push(node);
		if (node.getLeft() != null) {
			stack1.push(node.getLeft());
		}
		if (node.getRight() != null) {
			stack1.push(node.getRight());
		}
	}
	while (!stack2.isEmpty()) {
		Node<T> node = stack2.pop();
		System.out.print(node.getValue() + " ");
	}
}

层次遍历可以看成为先进先出的结果，利用队列来实现

// 层次遍历--利用队列实现，FIFO
public void levelTraverse(Node<T> node) {
	Queue<Node<T>> queue = new LinkedBlockingQueue<Node<T>>();
	queue.add(node);
	while (!queue.isEmpty()) {
		Node<T> temp = queue.poll();
		if (temp != null) {
			System.out.print(temp.getValue());
			if(temp.getLeft()!=null)
　　　　　　　　　　　　　　　　queue.add(temp.getLeft());
			if(temp.getRight())
　　　　　　　　　　　　　　　　queue.add(temp.getRight());
		}
	}
}