# Maximum Depth of Binary Tree

ID: 104; easy

## Solution 1 (Golang)

``````/**
* Definition for a binary tree node.
* type TreeNode struct {
*     Val int
*     Left *TreeNode
*     Right *TreeNode
* }
*/
func maxDepth(root *TreeNode) int {
if root == nil {
return 0
}
return max(maxDepth(root.Left), maxDepth(root.Right)) + 1
}

func max(x, y int) int {
if x > y {
return x
}
return y
}``````

## Solution 2 (Java)

``````/**
* Definition of TreeNode:
* public class TreeNode {
*     public int val;
*     public TreeNode left, right;
*     public TreeNode(int val) {
*         this.val = val;
*         this.left = this.right = null;
*     }
* }
*/

public class Solution {
/**
* @param root: The root of binary tree.
* @return: An integer
*/
public int maxDepth(TreeNode root) {
if (root == null) return 0;
return Math.max(maxDepth(root.left), maxDepth(root.right)) + 1;
}
}``````

### Notes

• Recursion with divide and conquer

## Solution 3 (Java)

``````/**
* Definition of TreeNode:
* public class TreeNode {
*     public int val;
*     public TreeNode left, right;
*     public TreeNode(int val) {
*         this.val = val;
*         this.left = this.right = null;
*     }
* }
*/

public class Solution {

int maxDepth = 0;
/**
* @param root: The root of binary tree.
* @return: An integer
*/
public int maxDepth(TreeNode root) {
maxDepthHelper(root, 1);
return maxDepth;
}

private void maxDepthHelper(TreeNode root, int depth) {
if (root == null) return;
if (depth > maxDepth) maxDepth = depth;

maxDepthHelper(root.left, depth + 1);
maxDepthHelper(root.right, depth + 1);
}
}``````

### Notes

• Recursion with traversal

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