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.

思路

• 当前点的最大深度等于左右子节点最大深度加一

    public int maxDepth(TreeNode root) {
        // max{left's depth, right's depth} + 1
        if (root == null) {
            return 0;
        }
        int left = maxDepth(root.left);
        int right = maxDepth(root.right);

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