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.

要遍历所有点所以T:O(n)，S:O(height)递归深度

public int maxDepth(TreeNode root) {
    if (root == null) {
        return 0;
    }

    int left = maxDepth(root.left);
    int right = maxDepth(root.right);

    return Math.max(left, right) + 1;
}