JavaScript刷LeetCode -- 814. Binary Tree Pruning【Medium】

一、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.)

二、题目大意

  给定一个二叉树，如果二叉树的子树中不包含1则删除，返回新的子树。

三、解题思路

  采用递归的方法，在递归的过程中，需要判断当前子树是保留还是删除：

  (root.val == 1 || root.left != null || root.right != null) ? root : null

四、代码实现

const pruneTree = root => {
  if (!root) {
    return null
  }
  root.left = pruneTree(root.left)
  root.right = pruneTree(root.right)
  return (root.val == 1 || root.left != null || root.right != null) ? root : null
}

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