Minimum Depth of Binary Tree

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 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;
        if(root.left==null) return minDepth(root.right)+1;
        if(root.right==null) return minDepth(root.left)+1;
        else{
            int left = minDepth(root.left);
            int right = minDepth(root.right);
            return (left<right?left:right)+1;
        }
    }
}