Get Min Depth of Binary Tree from Root

GetMinDepthBinaryTree.java

/**
 * Definition for binary tree
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public int minDepth(TreeNode root) {
        if (root == null) return 0;
        
        return minDepthHelper(root, 1);
        
    }
    
     public int minDepthHelper(TreeNode node, int level){
        if (node.left == null && node.right == null){
            return level;
        }
        
        int left = 0;
        int right = 0;
        int retVal = 0;
        
        if (node.left != null && node.right != null){
            left = minDepthHelper(node.left, level + 1);
            right = minDepthHelper(node.right, level + 1);
            return Math.min(left, right);
        }
        
        if (node.left != null)
            retVal = minDepthHelper(node.left, level + 1);
        
        if (node.right != null)
            retVal = minDepthHelper(node.right, level + 1);
            
        return retVal;
        
    }
}