Jun 23, 2022 · May 23, 2022 · May 23, 2022 · May 23, 2022 · May 23, 2022 · May 23, 2022
diff --git a/problems/0222.完全二叉树的节点个数.md b/problems/0222.完全二叉树的节点个数.md
Original file line number	Diff line number	Diff line change
Expand Up		@@ -646,5 +646,68 @@ func countNodes(_ root: TreeNode?) -> Int {
		}
		```

	## Scala

	递归:
	```scala
	object Solution {
	def countNodes(root: TreeNode): Int = {
	if(root == null) return 0
	1 + countNodes(root.left) + countNodes(root.right)
	}
	}
	```

	层序遍历:
	```scala
	object Solution {
	import scala.collection.mutable
	def countNodes(root: TreeNode): Int = {
	if (root == null) return 0
	val queue = mutable.Queue[TreeNode]()
	var node = 0
	queue.enqueue(root)
	while (!queue.isEmpty) {
	val len = queue.size
	for (i <- 0 until len) {
	node += 1
	val curNode = queue.dequeue()
	if (curNode.left != null) queue.enqueue(curNode.left)
	if (curNode.right != null) queue.enqueue(curNode.right)
	}
	}
	node
	}
	}
	```

	利用完全二叉树性质:
	```scala
	object Solution {
	def countNodes(root: TreeNode): Int = {
	if (root == null) return 0
	var leftNode = root.left
	var rightNode = root.right
	// 向左向右往下探
	var leftDepth = 0
	while (leftNode != null) {
	leftDepth += 1
	leftNode = leftNode.left
	}
	var rightDepth = 0
	while (rightNode != null) {
	rightDepth += 1
	rightNode = rightNode.right
	}
	// 如果相等就是一个满二叉树
	if (leftDepth == rightDepth) {
	return (2 << leftDepth) - 1
	}
	// 如果不相等就不是一个完全二叉树,继续向下递归
	countNodes(root.left) + countNodes(root.right) + 1
	}
	}
	```

		-----------------------
		<div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>