1325

1325. Delete Leaves With a Given Value (Medium)

Given a binary tree root and an integer target, delete all the leaf nodes with value target.

Note that once you delete a leaf node with value target, if it's parent node becomes a leaf node and has the value target, it should also be deleted (you need to continue doing that until you can't).

 

Example 1:

Input: root = [1,2,3,2,null,2,4], target = 2
Output: [1,null,3,null,4]
Explanation: Leaf nodes in green with value (target = 2) are removed (Picture in left). 
After removing, new nodes become leaf nodes with value (target = 2) (Picture in center).

Example 2:

Input: root = [1,3,3,3,2], target = 3
Output: [1,3,null,null,2]

Example 3:

Input: root = [1,2,null,2,null,2], target = 2
Output: [1]
Explanation: Leaf nodes in green with value (target = 2) are removed at each step.

Example 4:

Input: root = [1,1,1], target = 1
Output: []

Example 5:

Input: root = [1,2,3], target = 1
Output: [1,2,3]

 

Constraints:

• 1 <= target <= 1000
• Each tree has at most 3000 nodes.
• Each node's value is between [1, 1000].

Related Topics:
Tree

Solution 1.

// OJ: https://leetcode.com/problems/delete-leaves-with-a-given-value/
// Author: github.com/lzl124631x
// Time: O(N)
// Space: O(H)
class Solution {
private:
    TreeNode* postorder(TreeNode *node, int target) {
        if (!node) return NULL;
        node->left = postorder(node->left, target);
        node->right = postorder(node->right, target);
        return !node->left && !node->right && node->val == target ? NULL : node;
    }
public:
    TreeNode* removeLeafNodes(TreeNode* root, int target) {
        return postorder(root, target);
    }
};