【LeetCode】二叉树剪枝搜索（Binary Tree Pruning）

原题网址(中)：https://leetcode-cn.com/problems/binary-tree-pruning/
原题网址(英)：https://leetcode.com/problems/binary-tree-pruning/

题目：

We are given the head node root of a binary tree, where additionally every node’s value is either a 0 or a 1.
Return the same tree where every subtree (of the given tree) not containing a 1 has been removed.
(Recall that the subtree of a node X is X, plus every node that is a descendant of X.).

给定二叉树根结点 root ，此外树的每个结点的值要么是 0，要么是 1。
返回移除了所有不包含 1 的子树的原二叉树
( 节点 X 的子树为 X 本身，以及所有 X 的后代。)

示例：

输入: [1,null,0,0,1]
输出: [1,null,0,null,1]

思路：

简单的递归思想。

代码:

public class Prob814_binary_tree_pruning {

  public TreeNode pruneTree(TreeNode root) {
    if(root.left != null)
      root.left = pruneTree(root.left);
    if(root.right != null)
      root.right = pruneTree(root.right);
    if(root.left == null && root.right == null && root.val == 0)
      return null;
    return root;
  }
}