二叉树的层序遍历

 

public class Application {

    static class Node {
        int val;
        Node left;
        Node right;

        public Node(int val) {
            this.val = val;
        }
    }


    public static void levelOrderTraversal (Node node) {
        Queue<Node> queue = new LinkedList<>();
        // 添加一个元素
        queue.offer(node);
        while (!queue.isEmpty()) {
            // 移除并返回队列头部元素, 为空返回null
            node = queue.poll();
            System.out.print(node.val + " ");

            if (node.left != null) {
                // 添加左节点元素
                queue.offer(node.left);
            }

            if (node.right != null) {
                // 添加右节点元素
                queue.offer(node.right);
            }
        }
    }

    public static void main(String[] args) {
        Node root = new Node(1);

        Node l1 = new Node(2);
        Node r1 = new Node(3);
        root.left = l1;
        root.right = r1;

        l1.left = new Node(4);
        l1.right = new Node(5);

        r1.left = new Node(6);
        r1.right = new Node(7);

        levelOrderTraversal(root);
    }
}