111. Minimum Depth of Binary Tree

/**
 * 111.Minimum Depth of Binary Tree 
 *
 * Problem Description:
 * Given a binary tree, find its minimum depth.
 * The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.
 *
 * Definition for a binary tree node.
 * 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;  
        if(root.left == null) return minDepth(root.right) + 1;  
        if(root.right == null) return minDepth(root.left) + 1;  
        return Math.min(minDepth(root.left), minDepth(root.right)) + 1;  
    }
}