牛客网：NC169 修剪叶子

import java.util.*;

/*
 * public class TreeNode {
 *   int val = 0;
 *   TreeNode left = null;
 *   TreeNode right = null;
 *   public TreeNode(int val) {
 *     this.val = val;
 *   }
 * }
 */

public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param root TreeNode类 
     * @return TreeNode类
     */
    public TreeNode pruneLeaves (TreeNode root) {
        // write code here
        if (root == null) return null;
        if (root.left != null && root.left.left == null && root.left.right == null) return null;
        if (root.right != null && root.right.left == null && root.right.right == null) return null;
        root.left = pruneLeaves(root.left);
        root.right = pruneLeaves(root.right);
        return root;
    }
}