题目链接:https://leetcode.com/problems/binary-tree-pruning/description/
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.)
Example 1: Input: [1,null,0,0,1] Output: [1,null,0,null,1] Explanation: Only the red nodes satisfy the property "every subtree not containing a 1". The diagram on the right represents the answer.Example 2: Input: [1,0,1,0,0,0,1] Output: [1,null,1,null,1]Example 3: Input: [1,1,0,1,1,0,1,0] Output: [1,1,0,1,1,null,1]Note:
- The binary tree will have at most
100 nodes
.- The value of each node will only be
0
or1
.
题目解析:大意就是删掉值为0且以此节点为根的子树中无1的节点。很容易想到用递归来处理,自下而上删除节点,处理好判断条件即可。
代码如下:0ms Accepted beating 100%
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
TreeNode* pruneTree(TreeNode* root) {
if (root == NULL)
return NULL;
root->left = pruneTree(root->left);
root->right = pruneTree(root->right);
if (root->val == 0 && root->left == NULL && root->right == NULL)
{
free(root);
return NULL;
}
return root;
}
};