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# 04/06/2022 104. Max depth of binary tree

BFS

```
// Some code
class Solution {
    public int maxDepth(TreeNode root) {
        if (root == null) return 0;
        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        int depth = 0;
        while (!queue.isEmpty()){
            int size = queue.size();
            depth++;
            for (int i = 0; i < size; i++){
                TreeNode curr = queue.poll();
                if (curr.left != null) queue.offer(curr.left);
                if (curr.right != null) queue.offer(curr.right);
            }
        }
        return depth;
    }
}
```

```
// Some code
class Solution {
    public int maxDepth(TreeNode root) {
        if (root == null) return 0;
        int left = maxDepth(root.left);
        int right = maxDepth(root.right);
        return 1 + Math.max(left, right);
        
    }
}
```