Finding max depth of binary tree without recursion

Question

Recursive mechanism to find max depth of depth of binary tree is very straightforward, but how can we do it efficiently without recursion as I have large tree where I would

Answer 1

I have written following logic to do find max and min depth which doesn't involve recursion and without increasing the space complexity.

// Find the maximum depth in the tree without using recursion
private static int maxDepthNoRecursion(TreeNode root) {
    return Math.max(maxDepthNoRecursion(root, true), maxDepthNoRecursion(root, false)); 
}

// Find the minimum depth in the tree without using recursion
private static int minDepthNoRecursion(TreeNode root) {
    return Math.min(maxDepthNoRecursion(root, true), maxDepthNoRecursion(root, false)); 
}

private static int maxDepthNoRecursion(TreeNode root, boolean left) {
    Stack stack = new Stack<>();
    stack.add(root);
    int depth = 0;
    while (!stack.isEmpty()) {
        TreeNode node = stack.pop();
        if (left && node.left != null) stack.add(node.left);
        // Add the right node only if the left node is empty to find max depth
        if (left && node.left == null && node.right != null) stack.add(node.right); 
        if (!left && node.right != null) stack.add(node.right);
        // Add the left node only if the right node is empty to find max depth
        if (!left && node.right == null && node.left != null) stack.add(node.left);
        depth++;
    }
    return depth;
}