Sum of Left Leaves

code

/**
 * 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:
    int sumOfLeftLeaves(TreeNode* root) {
        if(root == NULL)
        {
            return 0;
        }

        return helper(root->left, true) + helper(root->right, false);

    }

    int helper(TreeNode* root, bool bLeft)
    {
        if(root == NULL)
        {
            return 0;
        }

        if(bLeft && root->left == NULL && root->right == NULL)
        {
            return root->val;
        }

        int left = helper(root->left, true);
        int right = helper(root->right, false);

        return left+right;
    }
};