L104. Maximum Depth of Binary Tree

Problem:

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.

Solution:

• minimum steps from top to the null bottom

• steps +1 will be the maximum level

public int maxDepth(TreeNode root) {
        if(root == null) return 0;
        int leftHeight = maxDepth(root.left);
        int rightHeight = maxDepth(root.right);
        
        return Math.max(leftHeight, rightHeight) + 1;
        
        
    }