104. Maximum Depth of Binary Tree

Description

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.

Answer

type TreeNode struct {
      Val int
      Left *TreeNode
      Right *TreeNode
  }
var deap int

func dfs(root *TreeNode,d int){
    if root == nil{
        if d > deap{
            deap =d
        }
        return
    }
    dfs(root.Left,d+1)
    dfs(root.Right,d+1)
}

func maxDepth(root *TreeNode) int {
    deap = -1
    dfs(root,0)
    return deap    
}