111 二叉树的最小深度

111 二叉树的最小深度

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