0104-maximum-depth-of-binary-tree.kt

importjava.util.*

/**
 * Example:
 * var ti = TreeNode(5)
 * var v = ti.`val`
 * Definition for a binary tree node.
 * class TreeNode(var `val`: Int) {
 * var left: TreeNode? = null
 * var right: TreeNode? = null
 * }
*/
classSolution {
funmaxDepth(root:TreeNode?): Int {
if (root ==null)
return0

val left = maxDepth(root.left)
val right = maxDepth(root.right)

return1+Math.max(left, right)
 }

funiterativeMaxDepth(root:TreeNode?): Int {
if (root ==null) return0
val callStack =Stack<Pair<TreeNode, Int>>().apply { add(Pair(root, 1)) }
var currentMaxDepth =1
var temp:Pair<TreeNode, Int>
while (callStack.isNotEmpty()) {
 temp = callStack.pop()
 currentMaxDepth = maxOf(currentMaxDepth, temp.second)
with(temp.first) {
 left?.let { callStack.add(Pair(it, currentMaxDepth +1)) }
 right?.let { callStack.add(Pair(it, currentMaxDepth +1)) }
 }
 }
return currentMaxDepth
 }
}