【剑指offer-Java版】23从上往下打印二叉树

public class _Q23 {

public <T> void PrintTreeFromTopToButtom(BinaryTreeNode<T> root){
if(root == null) return;

Queue<BinaryTreeNode<T>> queue = new LinkedList<>();

queue.add(root);
while(!queue.isEmpty()){
BinaryTreeNode<T> node = queue.remove();

if(node.leftChild != null) queue.add(node.leftChild);
if(node.rightChild != null) queue.add(node.rightChild);

System.out.print(node.value + " ");
}
System.out.println();
}
}

public class _Q23Test extends TestCase {

_Q23 tree = new _Q23();

public void test(){
BinaryTreeNode<Integer> root = new BinaryTreeNode<>();
BinaryTreeNode<Integer> node1 = new BinaryTreeNode<>();
BinaryTreeNode<Integer> node2 = new BinaryTreeNode<>();
BinaryTreeNode<Integer> node3 = new BinaryTreeNode<>();
BinaryTreeNode<Integer> node4 = new BinaryTreeNode<>();
BinaryTreeNode<Integer> node5 = new BinaryTreeNode<>();
BinaryTreeNode<Integer> node6 = new BinaryTreeNode<>();

root.value = 8;
node1.value = 6;
node2.value = 10;
node3.value = 5;
node4.value = 7;
node5.value = 9;
node6.value = 11;

root.leftChild = node1;
root.rightChild = node2;
node1.leftChild = node3;
node1.rightChild = node4;
node2.leftChild = node5;
node2.rightChild = node6;

node3.leftChild = null; node3.rightChild = null;
node4.leftChild = null; node4.rightChild = null;
node5.leftChild = null; node5.rightChild = null;
node6.leftChild = null; node6.rightChild = null;

tree.PrintTreeFromTopToButtom(root);
tree.PrintTreeFromTopToButtom(null);
tree.PrintTreeFromTopToButtom(node1);
}
}