Swift-二叉树的最大深度与最小深度

题目：输入一棵二叉树的根节点，求该树的深度。从根节点到叶子结点一次经过的结点形成树的一条路径，最长路径的长度为树的深度。根节点的深度为1.

最大深度

`
 
 
func treeMaxDepth(rootNode:TreeNode?) -> Int {
    if rootNode == nil {
        return 0
    }
    
    let leftDepth:Int = treeMaxDepth(rootNode: rootNode?.leftChild)
    let rightDepth:Int = treeMaxDepth(rootNode: rootNode?.rightChild)
    
    return leftDepth > rightDepth ? leftDepth + 1 : rightDepth + 1
}`

最小深度

最小深度： 从根节点开始到叶子节点结束的最短路径上的节点数，递归解决过程:
①空树最小深度是0.
②左子树空： 右子树最小深度+ 1
③右子树空： 左子树最小深度 + 1
④min(左子树最小深度，右子树最小深度) + 1

`
 func treeMinDepth(rootNode:TreeNode?) -> Int {
 if rootNode == nil {
 return 0
 }
 
 
    let leftDepth:Int = treeMinDepth(rootNode: rootNode?.leftChild)
    let rightDepth:Int = treeMinDepth(rootNode: rootNode?.rightChild)
    
    if leftDepth == 0 {
        return rightDepth + 1
    }
    
    if rightDepth == 0 {
        return leftDepth + 1
    }
    
    return leftDepth < rightDepth ? leftDepth + 1 : rightDepth + 1
}`

测试代码:

`
 
 
var util:TreeUtil = TreeUtil()
 var depthData:[String] = ["1","2","4","#","#","5","7","#","#","#","3","#","6","#","#"]
 var preRootNode:TreeNode?
 util.createTreeByPreOrderData(root: &preRootNode, listData: depthData)
 var binaryTreePath:BinaryTreePath = BinaryTreePath()
 var binaryDepth:Int = binaryTreePath.treeMaxDepth(rootNode: preRootNode)
 print("FlyElephant-最大深度--(binaryDepth)")
 
 
var binaryMinDepth:Int = binaryTreePath.treeMinDepth(rootNode: preRootNode)
 print("FlyElephant-最小深度--(binaryMinDepth)")`