Today I have done leetcode's May LeetCoding Challenge with cpp.

May LeetCoding Challenge 17

Description

Delete Leaves With a Given Value

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 its parent node becomes a leaf node and has the value target, it should also be deleted (you need to continue doing that until you cannot).

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.

Constraints:

• The number of nodes in the tree is in the range [1, 3000].
• 1 <= Node.val, target <= 1000

Solution

class Solution {
public:
  TreeNode* removeLeafNodes(TreeNode* root, int target) {
    if(!root) return nullptr;
    root->left = removeLeafNodes(root->left, target);
    root->right = removeLeafNodes(root->right, target);
    if(!root->left && !root->right && root->val == target) return nullptr;
    return root;
  }
};