path-sum.cpp

// https://leetcode.com/problems/path-sum/

/**
 * 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 dfs(TreeNode *node, int currentSum, int targetSum)
	{
		if (node == nullptr)
		{
			return false;
		}

		currentSum += node->val;

		if (node->left == nullptr && node->right == nullptr)
		{
			return (currentSum == targetSum);
		}

		return (dfs(node->left, currentSum, targetSum) ||
				dfs(node->right, currentSum, targetSum));
	}

	bool hasPathSum(TreeNode *root, int targetSum)
	{
		return dfs(root, 0, targetSum);
	}
};