Path Sum

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

Solution: Recursion

bool hasPathSum(TreeNode* root, int sum) {
    if (!root) return false;
    if (!root->left && !root->right) return root->val == sum;
    return hasPathSum(root->left, sum - root->val) || hasPathSum(root->right, sum - root->val);
}