Java实现LeetCode 111. Minimum Depth of Binary Tree

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