104.maximum-depth-of-binary-tree.md

104. Maximum Depth of Binary Tree

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.

JavaScript

/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @return {number}
 */
var maxDepth = function(root) {    
    return maxDepthHelper(root,0);
    
};

var maxDepthHelper = function(root, depth){
    if(root !==null){
        depth = 1 + depth;
    }else{
        return depth;
    }
    let leftDepth = maxDepthHelper(root.left,depth);
    let rigthDepth = maxDepthHelper(root.right,depth);
    
    
    if(leftDepth > rigthDepth){
        return leftDepth;
    }
    return rigthDepth;
}