Leetcode #104 Maximum Depth of Binary Tree

This question can be solved via recursion depth first search. Keep track of the max depth. Traverse left sub tree then traverse right sub tree - increase the depth each level.

Link: Maximum Depth of Binary Tree

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

    let dfs = (node, lvl) => {
        if(!node) return;
        if(lvl>max){
            max = lvl;
        }

        if(node.left){
            dfs(node.left, lvl+1);
        }

        if(node.right){
            dfs(node.right, lvl+1);
        }
    };

    dfs(root, 1);
    return max;
};