559. Maximum Depth of N-ary Tree

Easy

Given a n-ary 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.

Nary-Tree input serialization is represented in their level order traversal, each group of children is separated by the null value (See examples).

Example 1:

Input: root = [1,null,3,2,4,null,5,6]
Output: 3

Example 2:

Input: root = [1,null,2,3,4,5,null,null,6,7,null,8,null,9,10,null,null,11,null,12,null,13,null,null,14]
Output: 5

Constraints:

• The total number of nodes is in the range [0, 10^4].

• The depth of the n-ary tree is less than or equal to 1000.

解題

/**
 * Definition for a Node.
 * type Node struct {
 *     Val int
 *     Children []*Node
 * }
 */

func maxDepth(root *Node) int {
    ans := 0

    var dfs func(*Node, int)
    dfs = func(r *Node, depth int) {
        if r == nil { return }

        if depth + 1 > ans { ans = depth + 1 }

        for _, child := range r.Children {
            dfs(child, depth + 1)
        }
    }

    dfs(root, 0)

    return ans
}