A nice binary tree problem by using recursion

Recursion is a powerful method if you know how to use it properly.

A nice binary tree problem can be found:

814. Binary Tree Pruning

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    TreeNode* pruneTree(TreeNode* root) {
        if (root == nullptr) return nullptr;
        root -> left = pruneTree(root -> left);
        root -> right = pruneTree(root -> right);
        if (root -> val == 1 || root -> left || root -> right)return root;
        return nullptr;
    }
};

Pretty nice, right? Thanks for reading.