112.path-sum.cpp

/*
 * @lc app=leetcode id=112 lang=cpp
 *
 * [112] Path Sum
 *
 * https://leetcode.com/problems/path-sum/description/
 *
 * algorithms
 * Easy (37.04%)
 * Total Accepted:    286.9K
 * Total Submissions: 774.7K
 * Testcase Example:  '[5,4,8,11,null,13,4,7,2,null,null,null,1]\n22'
 *
 * Given a binary tree and a sum, determine if the tree has a root-to-leaf path
 * such that adding up all the values along the path equals the given sum.
 *
 * Note: A leaf is a node with no children.
 *
 * Example:
 *
 * Given the below binary tree and sum = 22,
 *
 *
 * ⁠     5
 * ⁠    / \
 * ⁠   4   8
 * ⁠  /   / \
 * ⁠ 11  13  4
 * ⁠/  \      \
 * 7    2      1
 *
 *
 * return true, as there exist a root-to-leaf path 5->4->11->2 which sum is 22.
 *
 */
#include <vector>

struct TreeNode
{
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode(int x) : val(x), left(NULL), right(NULL) {}
};
class Solution
{
  public:
    bool hasPathSum(TreeNode *root, int sum)
    {
        if (!root)
            return false;
        if (!root->left && !root->right && (sum - root->val) == 0)
            return true;
        return (hasPathSum(root->left, sum - root->val) || hasPathSum(root->right, sum - root->val));
    }
};