[数据结构与算法]二叉树层序遍历（java版）

对二叉树进行层序遍历

二叉树定义

lass TreeNode{
    int val;
    TreeNode left;
    TreeNode right;
    TreeNode(int x) {
        val = x;
    }
}

使用队列进行层序遍历

 public static void traverse_level(TreeNode root){
            Queue<TreeNode> queue = new LinkedList<>();
            if(root!=null) queue.offer(root) ;
            while (!queue.isEmpty()){
                root = queue.poll();
                System.out.println(root.val);
                if(root.left!=null){
                    queue.offer(root.left);
                }
                if(root.right!=null){
                    queue.offer(root.right);
                }} }

测试

public static void main(String[] args) {
TreeNode root1 = new TreeNode(3);
        root1.left=new TreeNode(9);
        root1.right=new TreeNode(20);
        root1.right.left= new TreeNode(15);
        root1.right.right= new TreeNode(7);
        traverse_level(root1);
}

结果

3-9-20-15-7