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.

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