112_PathSum.cpp

//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.

//For 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.

/**
 * Definition for a binary tree node.
 * 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 == NULL) return false;
        if(root->val == sum && root->left == NULL && root->right == NULL) return true;
        
        return hasPathSum(root->left, sum-root->val) || hasPathSum(root->right, sum-root->val);

    }
};