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 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:

/**
 * Definition for a binary tree node.
 * class TreeNode {
 *     public $val = null;
 *     public $left = null;
 *     public $right = null;
 *     function __construct($val = 0, $left = null, $right = null) {
 *         $this->val = $val;
 *         $this->left = $left;
 *         $this->right = $right;
 *     }
 * }
 */
class Solution {

    /**
     * @param TreeNode $root
     * @param Integer $target
     * @return TreeNode
     */
    function removeLeafNodes($root, $target) {
        if ($root == null) return null;

        if ($root->left == null && $root->right == null && $root->val == $target)
            return null;

        $root->left = $this->removeLeafNodes($root->left, $target);
        $root->right = $this->removeLeafNodes($root->right, $target);

        if ($root->left == null && $root->right == null && $root->val == $target)
            return null;

        return $root;
    }
}

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