Given a binary tree, find its maximum depth.
The maximum depth is the number of nodes along the longest path from the root node down to the farthest leaf node.
Note: A leaf is a node with no children.
Example:
Given binary tree [3,9,20,null,null,15,7]
,
3
/ \
9 20
/ \
15 7
return its depth = 3.
Tags: Tree, Depth-first Search
题意是找到二叉树的最大深度,很明显,深搜即可,每深入一次节点加一即可,然后取左右子树的最大深度。
//Definition for a binary tree node.
public class TreeNode {
public var val: Int
public var left: TreeNode?
public var right: TreeNode?
public init(_ val: Int) {
self.val = val
self.left = nil
self.right = nil
}
}
func maxDepth(_ root: TreeNode?) -> Int {
if root == nil {
return 0;
}
return 1 + max(maxDepth(root?.left), maxDepth(root?.right))
}
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