<p>Given the <code>root</code> of a binary tree and an integer <code>targetSum</code>, return <code>true</code> if the tree has a <strong>root-to-leaf</strong> path such that adding up all the values along the path equals <code>targetSum</code>.</p>

<p>A <strong>leaf</strong> is a node with no children.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/01/18/pathsum1.jpg" style="width: 500px; height: 356px;" />
<pre>
<strong>Input:</strong> root = [5,4,8,11,null,13,4,7,2,null,null,null,1], targetSum = 22
<strong>Output:</strong> true
<strong>Explanation:</strong> The root-to-leaf path with the target sum is shown.
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/01/18/pathsum2.jpg" />
<pre>
<strong>Input:</strong> root = [1,2,3], targetSum = 5
<strong>Output:</strong> false
<strong>Explanation:</strong> There two root-to-leaf paths in the tree:
(1 --&gt; 2): The sum is 3.
(1 --&gt; 3): The sum is 4.
There is no root-to-leaf path with sum = 5.
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> root = [], targetSum = 0
<strong>Output:</strong> false
<strong>Explanation:</strong> Since the tree is empty, there are no root-to-leaf paths.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li>The number of nodes in the tree is in the range <code>[0, 5000]</code>.</li>
	<li><code>-1000 &lt;= Node.val &lt;= 1000</code></li>
	<li><code>-1000 &lt;= targetSum &lt;= 1000</code></li>
</ul>

/**
 * 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:
    bool hasPathSum(TreeNode* root, int targetSum) {
        if (!root) {
            return false;
        }

        return helper(root, targetSum);
    }

    bool helper(TreeNode* root, int targetSum) {
        if (!root) {
            return false;
        }

        targetSum -= root->val;

        if (!root->left && !root->right) {
            return targetSum == 0;
        }

        bool left = helper(root->left, targetSum);
        bool right = helper(root->right, targetSum);
        root->left = nullptr;
        root->right = nullptr;

        return left || right;
    }
};
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