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 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

• The given binary tree will have between 1 and 3000 nodes.

• Each node's value is between [1, 1000].

class Solution {
    public TreeNode removeLeafNodes(TreeNode root, int target) {
        if (root == null)
            return root;
        if (root.left == null && root.right == null) {
            if (root.val == target)
                return null;
            return root;
        }
        root.right = removeLeafNodes(root.right, target);
        root.left = removeLeafNodes(root.left, target);
        if (root.left == null && root.right == null && root.val == target)
            return null;
        return root;
    }
}